diff --git a/src/include/units/base_dimension.h b/src/include/units/base_dimension.h
index 73ce92c2..2df37dc4 100644
--- a/src/include/units/base_dimension.h
+++ b/src/include/units/base_dimension.h
@@ -22,8 +22,8 @@
 
 #pragma once
 
-#include <units/bits/fixed_string.h>
-#include <units/bits/unit_concept.h>
+#include <units/bits/external/fixed_string.h>
+#include <units/unit_concept.h>
 #include <type_traits>
 
 namespace units {
diff --git a/src/include/units/concepts.h b/src/include/units/bits/concepts.h
similarity index 95%
rename from src/include/units/concepts.h
rename to src/include/units/bits/concepts.h
index fcc16f35..b43d4524 100644
--- a/src/include/units/concepts.h
+++ b/src/include/units/bits/concepts.h
@@ -22,8 +22,8 @@
 
 #pragma once
 
-#include <units/bits/hacks.h>
-#include <units/bits/numeric_concepts.h>
+#include <units/bits/external/hacks.h>
+#include <units/bits/external/numeric_concepts.h>
 #include <units/customization_points.h>
 #include <units/ratio.h>
 
diff --git a/src/include/units/bits/deduced_symbol_text.h b/src/include/units/bits/deduced_symbol_text.h
new file mode 100644
index 00000000..04476b27
--- /dev/null
+++ b/src/include/units/bits/deduced_symbol_text.h
@@ -0,0 +1,82 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/bits/external/fixed_string.h>
+#include <units/bits/external/text_tools.h>
+#include <units/derived_dimension.h>
+
+namespace units::detail {
+
+template<bool Divide, std::size_t Idx>
+constexpr auto operator_text()
+{
+  if constexpr(Idx == 0) {
+    if constexpr(Divide) {
+      return basic_fixed_string("1/");
+    }
+    else {
+      return basic_fixed_string("");
+    }
+  }
+  else {
+    if constexpr(Divide) {
+      return basic_fixed_string("/");
+    }
+    else {
+      return basic_fixed_string("⋅");
+    }
+  }
+}
+
+template<typename E, basic_fixed_string Symbol, std::size_t Idx>
+constexpr auto exp_text()
+{
+  // get calculation operator + symbol
+  const auto txt = operator_text<E::num < 0, Idx>() + Symbol;
+  if constexpr(E::den != 1) {
+    // add root part
+    return txt + basic_fixed_string("^(") + regular<abs(E::num)>() + basic_fixed_string("/") + regular<E::den>() + basic_fixed_string(")");
+  }
+  else if constexpr(abs(E::num) != 1) {
+    // add exponent part
+    return txt + superscript<abs(E::num)>();
+  }
+  else {
+    return txt;
+  }
+}
+
+template<typename... Us, typename... Es, std::size_t... Idxs>
+constexpr auto deduced_symbol_text(derived_dimension<Es...>, std::index_sequence<Idxs...>)
+{
+  return (exp_text<Es, Us::symbol, Idxs>() + ...);
+}
+
+template<DerivedDimension Dim, Unit... Us>
+constexpr auto deduced_symbol_text()
+{
+  return deduced_symbol_text<Us...>(Dim(), std::index_sequence_for<Us...>());
+}
+
+}  // namespace units::detail
diff --git a/src/include/units/bits/deduced_unit.h b/src/include/units/bits/deduced_unit.h
new file mode 100644
index 00000000..6f170aa5
--- /dev/null
+++ b/src/include/units/bits/deduced_unit.h
@@ -0,0 +1,72 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/unit_of_concept.h>
+#include <units/derived_dimension.h>
+
+namespace units::detail {
+
+// same_scaled_units
+template<DerivedDimension D, Unit... Us>
+inline constexpr bool same_scaled_units = false;
+
+template<typename... Es, Unit... Us>
+inline constexpr bool same_scaled_units<derived_dimension<Es...>, Us...> = (UnitOf<Us, typename Es::dimension> && ...);
+
+// deduced_unit
+template<typename Result, int UnitExpNum, int UnitExpDen, typename UnitRatio>
+struct ratio_op;
+
+template<typename Result, int UnitExpDen, typename UnitRatio>
+struct ratio_op<Result, 0, UnitExpDen, UnitRatio> {
+  using ratio = Result;
+};
+
+template<typename Result, int UnitExpNum, int UnitExpDen, typename UnitRatio>
+struct ratio_op {
+  using calc_ratio =
+      conditional<(UnitExpNum * UnitExpDen > 0), ratio_multiply<Result, UnitRatio>, ratio_divide<Result, UnitRatio>>;
+  static constexpr int value = (UnitExpNum * UnitExpDen > 0) ? (UnitExpNum - UnitExpDen) : (UnitExpNum + UnitExpDen);
+  using ratio = ratio_op<calc_ratio, value, UnitExpDen, UnitRatio>::ratio;
+};
+
+template<DerivedDimension D, Unit... Us>
+struct derived_ratio;
+
+template<Unit... Us>
+struct derived_ratio<derived_dimension<>, Us...> {
+  using ratio = ::units::ratio<1>;
+};
+
+template<typename E, typename... ERest, Unit U, Unit... URest>
+struct derived_ratio<derived_dimension<E, ERest...>, U, URest...> {
+  using rest_ratio = derived_ratio<derived_dimension<ERest...>, URest...>::ratio;
+  using ratio = ratio_op<rest_ratio, E::num, E::den, typename U::ratio>::ratio;
+};
+
+template<DerivedDimension D, Unit... Us>
+using deduced_unit =
+    scaled_unit<typename D::coherent_unit::reference, typename detail::derived_ratio<typename D::recipe, Us...>::ratio>;
+
+}  // namespace units::detail
diff --git a/src/include/units/dimension_op.h b/src/include/units/bits/dimension_op.h
similarity index 98%
rename from src/include/units/dimension_op.h
rename to src/include/units/bits/dimension_op.h
index e18649e8..520086c8 100644
--- a/src/include/units/dimension_op.h
+++ b/src/include/units/bits/dimension_op.h
@@ -200,7 +200,7 @@ struct dimension_sqrt_impl;
 
 template<BaseDimension D>
 struct dimension_sqrt_impl<D> {
-  using type = derived_dimension<exp<D, 1, 2>>;
+  using type = downcast_dimension<derived_dimension<exp<D, 1, 2>>>;
 };
 
 template<BaseDimension D>
@@ -210,7 +210,7 @@ struct dimension_sqrt_impl<derived_dimension<exp<D, 2>>> {
 
 template<DerivedDimension D>
 struct dimension_sqrt_impl<D> {
-  using type = dimension_sqrt_impl<typename D::downcast_base_type>;
+  using type = dimension_sqrt_impl<typename D::downcast_base_type>::type;
 };
 
 template<typename... Es>
@@ -221,7 +221,7 @@ struct dimension_sqrt_impl<derived_dimension<Es...>> {
 }  // namespace detail
 
 template<Dimension D>
-using dimension_sqrt = detail::dimension_sqrt_impl<typename D::downcast_base_type>::type;
+using dimension_sqrt = detail::dimension_sqrt_impl<D>::type;
 
 // dimension_pow
 namespace detail {
diff --git a/src/include/units/bits/downcasting.h b/src/include/units/bits/external/downcasting.h
similarity index 98%
rename from src/include/units/bits/downcasting.h
rename to src/include/units/bits/external/downcasting.h
index 822bf909..535147e9 100644
--- a/src/include/units/bits/downcasting.h
+++ b/src/include/units/bits/external/downcasting.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <units/bits/hacks.h>
+#include <units/bits/external/hacks.h>
 #include <type_traits>
 
 namespace units {
diff --git a/src/include/units/bits/fixed_string.h b/src/include/units/bits/external/fixed_string.h
similarity index 100%
rename from src/include/units/bits/fixed_string.h
rename to src/include/units/bits/external/fixed_string.h
diff --git a/src/include/units/bits/hacks.h b/src/include/units/bits/external/hacks.h
similarity index 100%
rename from src/include/units/bits/hacks.h
rename to src/include/units/bits/external/hacks.h
diff --git a/src/include/units/bits/numeric_concepts.h b/src/include/units/bits/external/numeric_concepts.h
similarity index 99%
rename from src/include/units/bits/numeric_concepts.h
rename to src/include/units/bits/external/numeric_concepts.h
index 5ccbe997..abbef656 100644
--- a/src/include/units/bits/numeric_concepts.h
+++ b/src/include/units/bits/external/numeric_concepts.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <units/bits/hacks.h>
+#include <units/bits/external/hacks.h>
 
 // P1813 - A Concept Design for the Numeric Algorithms
 
diff --git a/src/include/units/bits/external/text_tools.h b/src/include/units/bits/external/text_tools.h
new file mode 100644
index 00000000..7e102fe7
--- /dev/null
+++ b/src/include/units/bits/external/text_tools.h
@@ -0,0 +1,64 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/bits/external/fixed_string.h>
+
+namespace units::detail {
+
+template<int Value>
+  requires (0 <= Value) && (Value < 10)
+inline constexpr basic_fixed_string superscript_number = "";
+
+template<> inline constexpr basic_fixed_string superscript_number<0> = "\u2070";
+template<> inline constexpr basic_fixed_string superscript_number<1> = "\u00b9";
+template<> inline constexpr basic_fixed_string superscript_number<2> = "\u00b2";
+template<> inline constexpr basic_fixed_string superscript_number<3> = "\u00b3";
+template<> inline constexpr basic_fixed_string superscript_number<4> = "\u2074";
+template<> inline constexpr basic_fixed_string superscript_number<5> = "\u2075";
+template<> inline constexpr basic_fixed_string superscript_number<6> = "\u2076";
+template<> inline constexpr basic_fixed_string superscript_number<7> = "\u2077";
+template<> inline constexpr basic_fixed_string superscript_number<8> = "\u2078";
+template<> inline constexpr basic_fixed_string superscript_number<9> = "\u2079";
+
+template<int Value>
+  requires (Value >= 0)
+constexpr auto superscript()
+{
+  if constexpr(Value < 10)
+    return superscript_number<Value>;
+  else
+    return superscript<Value / 10>() + superscript<Value % 10>();
+}
+
+template<int Value>
+  requires (Value >= 0)
+constexpr auto regular()
+{
+  if constexpr(Value < 10)
+    return basic_fixed_string(static_cast<char>('0' + Value));
+  else
+    return regular<Value / 10>() + regular<Value % 10>();
+}
+
+}  // namespace units::detail
diff --git a/src/include/units/bits/type_list.h b/src/include/units/bits/external/type_list.h
similarity index 99%
rename from src/include/units/bits/type_list.h
rename to src/include/units/bits/external/type_list.h
index a4b51d6e..422bb00f 100644
--- a/src/include/units/bits/type_list.h
+++ b/src/include/units/bits/external/type_list.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <units/bits/type_traits.h>
+#include <units/bits/external/type_traits.h>
 
 namespace units {
 
diff --git a/src/include/units/bits/type_traits.h b/src/include/units/bits/external/type_traits.h
similarity index 100%
rename from src/include/units/bits/type_traits.h
rename to src/include/units/bits/external/type_traits.h
diff --git a/src/include/units/bits/unit_text.h b/src/include/units/bits/unit_text.h
new file mode 100644
index 00000000..af95c30e
--- /dev/null
+++ b/src/include/units/bits/unit_text.h
@@ -0,0 +1,129 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/bits/deduced_symbol_text.h>
+#include <units/derived_dimension.h>
+
+namespace units::detail {
+
+template<typename Ratio>
+constexpr auto ratio_text()
+{
+  if constexpr(Ratio::num != 1 || Ratio::den != 1) {
+    auto txt = basic_fixed_string("[") + regular<Ratio::num>();
+    if constexpr(Ratio::den == 1) {
+      return txt + basic_fixed_string("]");
+    }
+    else {
+      return txt + basic_fixed_string("/") + regular<Ratio::den>() + basic_fixed_string("]");
+    }
+  }
+  else {
+    return basic_fixed_string("");
+  }
+}
+
+template<typename Ratio, typename PrefixType>
+constexpr auto prefix_or_ratio_text()
+{
+  if constexpr(Ratio::num == 1 && Ratio::den == 1) {
+    // no ratio/prefix
+    return basic_fixed_string("");
+  }
+  else {
+    if constexpr (!std::same_as<PrefixType, no_prefix>) {
+      // try to form a prefix
+      using prefix = downcast<detail::prefix_base<PrefixType, Ratio>>;
+
+      if constexpr(!std::same_as<prefix, prefix_base<PrefixType, Ratio>>) {
+        // print as a prefixed unit
+        return prefix::symbol;
+      }
+      else {
+        // print as a ratio of the coherent unit
+        return ratio_text<Ratio>();
+      }
+    }
+    else {
+      // print as a ratio of the coherent unit
+      return ratio_text<Ratio>();
+    }
+  }
+}
+
+template<typename... Es, std::size_t... Idxs>
+constexpr auto derived_dimension_unit_text(derived_dimension<Es...>, std::index_sequence<Idxs...>)
+{
+  return (exp_text<Es, dimension_unit<typename Es::dimension>::symbol, Idxs>() + ...);
+}
+
+template<typename... Es>
+constexpr auto derived_dimension_unit_text(derived_dimension<Es...> d)
+{
+  return derived_dimension_unit_text(d, std::index_sequence_for<Es...>());
+}
+
+template<typename... Es>
+constexpr bool all_named(derived_dimension<Es...>)
+{
+  return (dimension_unit<typename Es::dimension>::is_named && ...);
+}
+
+template<Dimension Dim>
+constexpr auto derived_dimension_unit_text()
+{
+  using recipe = typename Dim::recipe;
+  if constexpr(all_named(recipe()))
+    return derived_dimension_unit_text(recipe());
+  else
+    return derived_dimension_unit_text(Dim());
+}
+
+// TODO Inline below concept when switched to gcc-10
+template<typename T>
+concept has_symbol = requires{ T::symbol; };
+
+template<Dimension Dim, Unit U>
+constexpr auto unit_text()
+{
+  if constexpr(has_symbol<U>) {
+    // already has a symbol so print it
+    return U::symbol;
+  }
+  else {
+    // print as a prefix or ratio of a reference unit
+    auto prefix_txt = prefix_or_ratio_text<typename U::ratio, typename U::reference::prefix_type>();
+
+    if constexpr(has_symbol<typename U::reference>) {
+      // use predefined reference unit symbol
+      return prefix_txt + U::reference::symbol;
+    }
+    else {
+      // use derived dimension ingredients to create a unit symbol
+      return prefix_txt + derived_dimension_unit_text<Dim>();
+    }
+  }
+}
+
+}  // namespace units::detail
diff --git a/src/include/units/derived_dimension.h b/src/include/units/derived_dimension.h
index 42456975..a0846a81 100644
--- a/src/include/units/derived_dimension.h
+++ b/src/include/units/derived_dimension.h
@@ -23,9 +23,9 @@
 #pragma once
 
 #include <units/base_dimension.h>
-#include <units/bits/downcasting.h>
-#include <units/bits/fixed_string.h>
-#include <units/bits/type_list.h>
+#include <units/bits/external/downcasting.h>
+#include <units/bits/external/fixed_string.h>
+#include <units/bits/external/type_list.h>
 #include <units/ratio.h>
 #include <ratio>
 
@@ -264,7 +264,7 @@ using base_units_ratio = base_units_ratio_impl<D>::type;
  * The implementation is responsible for unpacking all of the dimensions into a list containing only base dimensions
  * and their factors and putting them to the other (private) units::derived_dimension class template partial
  * specialization.
- *  
+ * 
  * @note User should always use only this partial specialization to create derived dimensions.
  * 
  * @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
@@ -279,24 +279,4 @@ struct derived_dimension<Child, U, E, ERest...> : downcast_child<Child, typename
   using base_units_ratio = detail::base_units_ratio<typename downcast_child<Child, typename detail::make_dimension<E, ERest...>>::downcast_base_type>;
 };
 
-namespace detail {
-
-template<Dimension D>
-struct dimension_unit_impl;
-
-template<BaseDimension D>
-struct dimension_unit_impl<D> {
-  using type = D::base_unit;
-};
-
-template<DerivedDimension D>
-struct dimension_unit_impl<D> {
-  using type = D::coherent_unit;
-};
-
-}
-
-template<Dimension D>
-using dimension_unit = detail::dimension_unit_impl<D>::type;
-
 }  // namespace units
diff --git a/src/include/units/format.h b/src/include/units/format.h
index 1bbea90d..68c688cc 100644
--- a/src/include/units/format.h
+++ b/src/include/units/format.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <units/bits/customization_points.h>
+#include <units/customization_points.h>
 #include <units/quantity.h>
 #include <fmt/format.h>
 #include <string_view>
@@ -116,20 +116,20 @@ namespace units {
       return format_to(out, treat_as_floating_point<Rep> ? "{:" + sign_text + "g}" : "{:" + sign_text + "}", val);
     }
 
-    template<typename Unit, typename OutputIt>
+    template<typename Dimension, typename Unit, typename OutputIt>
     inline static OutputIt format_units_quantity_unit(OutputIt out)
     {
-      return format_to(out, "{}", unit_text<Unit>().c_str());
+      return format_to(out, "{}", unit_text<Dimension, Unit>().c_str());
     }
 
-    template<typename OutputIt, typename Unit, typename Rep>
+    template<typename OutputIt, typename Dimension, typename Unit, typename Rep>
     struct units_formatter {
       OutputIt out;
       Rep val;
       fmt::sign_t sign;
       int precision;
 
-      explicit units_formatter(OutputIt o, quantity<Unit, Rep> q, fmt::sign_t s, int prec):
+      explicit units_formatter(OutputIt o, quantity<Dimension, Unit, Rep> q, fmt::sign_t s, int prec):
         out(o), val(q.count()), sign(s), precision(prec)
       {
       }
@@ -147,7 +147,7 @@ namespace units {
 
       void on_quantity_unit()
       {
-        out = format_units_quantity_unit<Unit>(out);
+        out = format_units_quantity_unit<Dimension, Unit>(out);
       }
     };
 
@@ -155,10 +155,10 @@ namespace units {
 
 }  // namespace units
 
-template<typename Unit, typename Rep, typename CharT>
-struct fmt::formatter<units::quantity<Unit, Rep>, CharT> {
+template<typename Dimension, typename Unit, typename Rep, typename CharT>
+struct fmt::formatter<units::quantity<Dimension, Unit, Rep>, CharT> {
 private:
-  using quantity = units::quantity<Unit, Rep>;
+  using quantity = units::quantity<Dimension, Unit, Rep>;
   using iterator = fmt::basic_parse_context<CharT>::iterator;
   using arg_ref_type = fmt::internal::arg_ref<CharT>;
 
@@ -293,7 +293,7 @@ public:
   }
 
   template<typename FormatContext>
-  auto format(const units::quantity<Unit, Rep>& q, FormatContext& ctx)
+  auto format(const units::quantity<Dimension, Unit, Rep>& q, FormatContext& ctx)
   {
     auto begin = format_str.begin(), end = format_str.end();
 
@@ -310,7 +310,7 @@ public:
       // default format should print value followed by the unit separeted with 1 space
       out = units::detail::format_units_quantity_value(out, q.count(), specs.sign, precision);
       *out++ = CharT(' ');
-      units::detail::format_units_quantity_unit<Unit>(out);
+      units::detail::format_units_quantity_unit<Dimension, Unit>(out);
     }
     else {
       // user provided format
diff --git a/src/include/units/physical/dimensions.h b/src/include/units/physical/dimensions.h
index 86004125..66460480 100644
--- a/src/include/units/physical/dimensions.h
+++ b/src/include/units/physical/dimensions.h
@@ -23,7 +23,7 @@
 #pragma once
 
 #include <units/base_dimension.h>
-#include <units/bits/type_traits.h>
+#include <units/bits/external/type_traits.h>
 #include <units/quantity.h>
 #include <units/unit.h>
 
diff --git a/src/include/units/prefix.h b/src/include/units/prefix.h
index 5f95b7e7..2117178d 100644
--- a/src/include/units/prefix.h
+++ b/src/include/units/prefix.h
@@ -22,8 +22,8 @@
 
 #pragma once
 
-#include <units/bits/downcasting.h>
-#include <units/bits/fixed_string.h>
+#include <units/bits/external/downcasting.h>
+#include <units/bits/external/fixed_string.h>
 #include <units/ratio.h>
 
 namespace units {
diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index 7bfa7375..0cf29bbf 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -22,8 +22,9 @@
 
 #pragma once
 
-#include <units/concepts.h>
-#include <units/dimension_op.h>
+#include <units/bits/concepts.h>
+#include <units/bits/dimension_op.h>
+#include <units/bits/unit_text.h>
 #include <limits>
 #include <ostream>
 
@@ -441,7 +442,7 @@ public:
   template<class CharT, class Traits>
   friend std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const quantity& q)
   {
-    return os << q.count(); // << " " << detail::unit_text<quantity::unit>(); TODO add support
+    return os << q.count() << " " << detail::unit_text<quantity::dimension, quantity::unit>();
   }
 };
 
diff --git a/src/include/units/ratio.h b/src/include/units/ratio.h
index 1092ca35..80e964f9 100644
--- a/src/include/units/ratio.h
+++ b/src/include/units/ratio.h
@@ -22,7 +22,7 @@
 
 #pragma once
 
-#include <units/bits/hacks.h>
+#include <units/bits/external/hacks.h>
 #include <type_traits>
 #include <numeric>
 #include <cstdint>
diff --git a/src/include/units/unit.h b/src/include/units/unit.h
index 2f9a3254..f0875a95 100644
--- a/src/include/units/unit.h
+++ b/src/include/units/unit.h
@@ -22,10 +22,13 @@
 
 #pragma once
 
-#include <units/bits/downcasting.h>
-#include <units/bits/fixed_string.h>
-#include <units/bits/type_traits.h>
-#include <units/bits/unit_concept.h>
+#include <units/bits/deduced_symbol_text.h>
+#include <units/bits/deduced_unit.h>
+#include <units/bits/external/downcasting.h>
+#include <units/bits/external/fixed_string.h>
+#include <units/bits/external/text_tools.h>
+#include <units/bits/external/type_traits.h>
+#include <units/unit_of_concept.h>
 #include <units/derived_dimension.h>
 #include <units/prefix.h>
 #include <units/ratio.h>
@@ -60,7 +63,7 @@ template<Unit U1, Unit U2>
 struct same_unit_reference : std::is_same<typename U1::reference, typename U2::reference> {};
 
 /**
- * @brief A starting point for a new hierarchy of units
+ * @brief An unnamed unit
  *
  * Defines a new unnamed (in most cases coherent) derived unit of a specific derived dimension
  * and it should be passed in this dimension's definition.
@@ -76,7 +79,7 @@ struct unit : downcast_child<Child, scaled_unit<Child, ratio<1>>> {
 /**
  * @brief Unknown unit
  * 
- * Used as a reference unit of an unknown dimension.
+ * Used as a coherent unit of an unknown dimension.
  */
 struct unknown_unit : unit<unknown_unit> {};
 
@@ -144,65 +147,13 @@ struct prefixed_unit :
   using prefix_type = P::prefix_type;
 };
 
-// UnitOf
-template<typename U, typename D>
-concept UnitOf =
-  Unit<U> &&
-  Dimension<D> &&
-  std::same_as<typename U::reference, typename dimension_unit<D>::reference>;
-
-namespace detail {
-
-// same_scaled_units
-template<DerivedDimension D, Unit... Us>
-inline constexpr bool same_scaled_units = false;
-
-template<typename... Es, Unit... Us>
-inline constexpr bool same_scaled_units<derived_dimension<Es...>, Us...> = (UnitOf<Us, typename Es::dimension> && ...);
-
-// deduced_unit
-template<typename Result, int UnitExpNum, int UnitExpDen, typename UnitRatio>
-struct ratio_op;
-
-template<typename Result, int UnitExpDen, typename UnitRatio>
-struct ratio_op<Result, 0, UnitExpDen, UnitRatio> {
-  using ratio = Result;
-};
-
-template<typename Result, int UnitExpNum, int UnitExpDen, typename UnitRatio>
-struct ratio_op {
-  using calc_ratio =
-      conditional<(UnitExpNum * UnitExpDen > 0), ratio_multiply<Result, UnitRatio>, ratio_divide<Result, UnitRatio>>;
-  static constexpr int value = (UnitExpNum * UnitExpDen > 0) ? (UnitExpNum - UnitExpDen) : (UnitExpNum + UnitExpDen);
-  using ratio = ratio_op<calc_ratio, value, UnitExpDen, UnitRatio>::ratio;
-};
-
-template<DerivedDimension D, Unit... Us>
-struct derived_ratio;
-
-template<Unit... Us>
-struct derived_ratio<derived_dimension<>, Us...> {
-  using ratio = ::units::ratio<1>;
-};
-
-template<typename E, typename... ERest, Unit U, Unit... URest>
-struct derived_ratio<derived_dimension<E, ERest...>, U, URest...> {
-  using rest_ratio = derived_ratio<derived_dimension<ERest...>, URest...>::ratio;
-  using ratio = ratio_op<rest_ratio, E::num, E::den, typename U::ratio>::ratio;
-};
-
-template<DerivedDimension D, Unit... Us>
-using deduced_unit =
-    scaled_unit<typename D::coherent_unit::reference, typename detail::derived_ratio<typename D::recipe, Us...>::ratio>;
-
-}  // namespace detail
-
 /**
  * @brief A unit with a deduced ratio and symbol
  *
  * Defines a new unit with a deduced ratio and symbol based on the recipe from the provided
- * derived dimension. The number and order of provided units should match the recipe of
- * dimension.
+ * derived dimension. The number and order of provided units should match the recipe of the
+ * derived dimension. All of the units provided should also be a named ones so it is possible
+ * to create a deduced symbol text.
  *
  * @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
  * @tparam Dim a derived dimension recipe to use for deduction
@@ -214,7 +165,7 @@ template<typename Child, DerivedDimension Dim, Unit U, Unit... URest>
            (U::is_named && (URest::is_named && ... && true))
 struct deduced_unit : downcast_child<Child, detail::deduced_unit<Dim, U, URest...>> {
   static constexpr bool is_named = false;
-  static constexpr auto symbol = basic_fixed_string{""};  // detail::deduced_symbol_text<Dim, U, Us...>(); // TODO implement this
+  static constexpr auto symbol = detail::deduced_symbol_text<typename Dim::recipe, U, URest...>();
   using prefix_type = no_prefix;
 };
 
diff --git a/src/include/units/bits/unit_concept.h b/src/include/units/unit_concept.h
similarity index 96%
rename from src/include/units/bits/unit_concept.h
rename to src/include/units/unit_concept.h
index d8e675b3..9e250657 100644
--- a/src/include/units/bits/unit_concept.h
+++ b/src/include/units/unit_concept.h
@@ -22,11 +22,12 @@
 
 #pragma once
 
-#include <units/bits/type_traits.h>
+#include <units/bits/external/type_traits.h>
 #include <units/ratio.h>
 
 namespace units {
 
+// UnitRatio
 template<typename R>
 concept UnitRatio = Ratio<R> && (R::num * R::den > 0);
 
diff --git a/src/include/units/unit_of_concept.h b/src/include/units/unit_of_concept.h
new file mode 100644
index 00000000..143d4678
--- /dev/null
+++ b/src/include/units/unit_of_concept.h
@@ -0,0 +1,57 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <units/derived_dimension.h>
+
+namespace units {
+
+namespace detail {
+
+template<Dimension D>
+struct dimension_unit_impl;
+
+template<BaseDimension D>
+struct dimension_unit_impl<D> {
+  using type = D::base_unit;
+};
+
+template<DerivedDimension D>
+struct dimension_unit_impl<D> {
+  using type = D::coherent_unit;
+};
+
+} // namespace detail
+
+template<Dimension D>
+using dimension_unit = detail::dimension_unit_impl<D>::type;
+
+// UnitOf
+template<typename U, typename D>
+concept UnitOf =
+  Unit<U> &&
+  Dimension<D> &&
+  std::same_as<typename U::reference, typename dimension_unit<D>::reference>;
+  // same_unit_reference<typename U, typename dimension_unit<D>> // TODO check if this works
+
+}  // namespace units
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 1a5b1883..67a1d088 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -20,6 +20,6 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-#add_subdirectory(unit_test/runtime)
+add_subdirectory(unit_test/runtime)
 add_subdirectory(unit_test/static)
 #add_subdirectory(metabench)
diff --git a/test/unit_test/runtime/digital_info_test.cpp b/test/unit_test/runtime/digital_info_test.cpp
index 600c17e6..0b032a09 100644
--- a/test/unit_test/runtime/digital_info_test.cpp
+++ b/test/unit_test/runtime/digital_info_test.cpp
@@ -20,43 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <units/quantity.h>
+#include <units/data/information.h>
 #include <catch2/catch.hpp>
 #include <sstream>
 
-namespace data {
+using namespace units::data;
 
-  struct base_dim_digital_information : units::base_dimension<"digital information", "b"> {};
-
-  struct digital_information : units::derived_dimension<digital_information, units::exp<base_dim_digital_information, 1>> {};
-
-  template<typename T>
-  concept DigitalInformation = units::QuantityOf<T, digital_information>;
-
-  struct data_prefix : units::prefix_type {};
-
-  struct kibi : units::prefix<kibi, data_prefix, units::ratio<    1'024>, "Ki"> {};
-  struct mebi : units::prefix<mebi, data_prefix, units::ratio<1'048'576>, "Mi"> {};
-
-  struct bit : units::named_coherent_derived_unit<bit, digital_information, "b", data_prefix> {};
-  struct kilobit : units::prefixed_derived_unit<kilobit, kibi, bit> {};
-  struct byte : units::named_scaled_derived_unit<byte, digital_information, "B", units::ratio<8>, data_prefix> {};
-  struct kilobyte : units::prefixed_derived_unit<kilobyte, kibi, byte> {};
-
-  inline namespace literals {
-
-    constexpr auto operator""_b(unsigned long long l) { return units::quantity<bit, std::int64_t>(l); }
-    constexpr auto operator""_Kib(unsigned long long l) { return units::quantity<kilobit, std::int64_t>(l); }
-    constexpr auto operator""_B(unsigned long long l) { return units::quantity<byte, std::int64_t>(l); }
-    constexpr auto operator""_KiB(unsigned long long l) { return units::quantity<kilobyte, std::int64_t>(l); }
-
-  }
-
-}
-
-using namespace data;
-
-TEST_CASE("operator<< on a custom quantity", "[text][ostream]")
+TEST_CASE("operator<< on a data quantity", "[text][ostream]")
 {
   std::stringstream stream;
 
@@ -64,25 +34,25 @@ TEST_CASE("operator<< on a custom quantity", "[text][ostream]")
   {
     SECTION("named unit")
     {
-      stream << 64_B;
+      stream << 64B;
       REQUIRE(stream.str() == "64 B");
     }
 
     SECTION("prefixed coherent unit")
     {
-      stream << 256_Kib;
+      stream << 256Kib;
       REQUIRE(stream.str() == "256 Kib");
     }
 
     SECTION("prefixed non-coherent unit")
     {
-      stream << 1024_KiB;
+      stream << 1024KiB;
       REQUIRE(stream.str() == "1024 KiB");
     }
 
     SECTION("other unit matching prefix")
     {
-      stream << 8_Kib * 8_Kib / 2_b;
+      stream << 8Kib * 8Kib / 2b;
       REQUIRE(stream.str() == "32 Mib");
     }
   }
diff --git a/test/unit_test/runtime/fmt_test.cpp b/test/unit_test/runtime/fmt_test.cpp
index a214bb6f..b3123215 100644
--- a/test/unit_test/runtime/fmt_test.cpp
+++ b/test/unit_test/runtime/fmt_test.cpp
@@ -20,18 +20,20 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/dimensions/area.h"
-#include "units/dimensions/frequency.h"
-#include "units/dimensions/power.h"
-#include "units/dimensions/velocity.h"
-#include "units/dimensions/volume.h"
-#include "units/dimensions/surface_tension.h"
+#include "units/physical/si/area.h"
+#include "units/physical/si/frequency.h"
+#include "units/physical/si/power.h"
+#include "units/physical/si/pressure.h"
+#include "units/physical/si/velocity.h"
+#include "units/physical/si/volume.h"
+#include "units/physical/si/surface_tension.h"
 #include "units/format.h"
 #include "units/math.h"
 #include <catch2/catch.hpp>
 #include <sstream>
 
 using namespace units;
+using namespace units::si;
 using namespace Catch::Matchers;
 
 TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
@@ -108,7 +110,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
   {
     SECTION("in terms of base units")
     {
-      const quantity<unit<length, ratio<1'000'000>>> q(123);
+      const length<scaled_unit<metre, ratio<1'000'000>>> q(123);
       stream << q;
 
       SECTION("iostream")
@@ -129,7 +131,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
     SECTION("in terms of derived units")
     {
-      const quantity<unit<energy, ratio<1, 100>>> q(60);
+      const energy<scaled_unit<joule, ratio<1, 100>>> q(60);
       stream << q;
 
       SECTION("iostream")
@@ -242,8 +244,8 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("surface tension")
       {
-        struct newton_per_centimetre : deduced_derived_unit<newton_per_centimetre, surface_tension, newton, centimetre> {};
-        const quantity<newton_per_centimetre> q(123);
+        struct newton_per_centimetre : deduced_unit<newton_per_centimetre, dim_surface_tension, newton, centimetre> {};
+        const surface_tension<newton_per_centimetre> q(123);
         stream << q;
 
         SECTION("iostream")
@@ -636,17 +638,17 @@ TEST_CASE("format string with only %Q should print quantity value only", "[text]
 
     SECTION("nan")
     {
-      CHECK(fmt::format("{:%Q}", quantity<metre>(std::numeric_limits<double>::quiet_NaN())) == "nan");
+      CHECK(fmt::format("{:%Q}", length<metre>(std::numeric_limits<double>::quiet_NaN())) == "nan");
     }
 
     SECTION("inf")
     {
-      CHECK(fmt::format("{:%Q}", quantity<metre>(std::numeric_limits<double>::infinity())) == "inf");
+      CHECK(fmt::format("{:%Q}", length<metre>(std::numeric_limits<double>::infinity())) == "inf");
     }
 
     SECTION("-inf")
     {
-      CHECK(fmt::format("{:%Q}", quantity<metre>(-std::numeric_limits<double>::infinity())) == "-inf");
+      CHECK(fmt::format("{:%Q}", length<metre>(-std::numeric_limits<double>::infinity())) == "-inf");
     }
   }
 }
@@ -742,8 +744,8 @@ TEST_CASE("fill and align specification", "[text][fmt]")
 
 TEST_CASE("sign specification", "[text][fmt]")
 {
-  quantity<metre> inf(std::numeric_limits<double>::infinity());
-  quantity<metre> nan(std::numeric_limits<double>::quiet_NaN());
+  length<metre> inf(std::numeric_limits<double>::infinity());
+  length<metre> nan(std::numeric_limits<double>::quiet_NaN());
 
   SECTION("default format {} on a quantity") 
   {
diff --git a/test/unit_test/runtime/fmt_units_test.cpp b/test/unit_test/runtime/fmt_units_test.cpp
index 390f8cb7..1e721528 100644
--- a/test/unit_test/runtime/fmt_units_test.cpp
+++ b/test/unit_test/runtime/fmt_units_test.cpp
@@ -20,16 +20,16 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/dimensions/area.h"
-#include "units/dimensions/frequency.h"
-#include "units/dimensions/power.h"
-#include "units/dimensions/velocity.h"
-#include "units/dimensions/volume.h"
-#include "units/dimensions/surface_tension.h"
+#include "units/physical/si/area.h"
+#include "units/physical/si/frequency.h"
+#include "units/physical/si/power.h"
+#include "units/physical/si/velocity.h"
+#include "units/physical/si/volume.h"
+#include "units/physical/si/surface_tension.h"
 #include "units/format.h"
 #include <catch2/catch.hpp>
 
-using namespace units;
+using namespace units::si;
 
 TEST_CASE("fmt::format on synthesized unit symbols", "[text][fmt]")
 {
diff --git a/test/unit_test/runtime/math_test.cpp b/test/unit_test/runtime/math_test.cpp
index 4e72e26b..b147e839 100644
--- a/test/unit_test/runtime/math_test.cpp
+++ b/test/unit_test/runtime/math_test.cpp
@@ -21,73 +21,35 @@
 // SOFTWARE.
 
 #include "units/math.h"
-#include "units/dimensions/area.h"
-#include "units/dimensions/volume.h"
+#include "units/physical/si/area.h"
+#include "units/physical/si/volume.h"
 #include <catch2/catch.hpp>
 
 using namespace units;
+using namespace units::si;
 
 // classical
 
-TEST_CASE("pow<N>() on quantity changes the value and the dimension accordingly", "[math][pow]")
+TEST_CASE("'pow<N>()' on quantity changes the value and the dimension accordingly", "[math][pow]")
 {
-  CHECK(pow<0>(2m) == 1);
-  CHECK(pow<1>(2m) == 2m);
-  CHECK(pow<2>(2m) == 4sq_m);
-  CHECK(pow<3>(2m) == 8cub_m);
+  SECTION ("'pow<0>(q)' returns '1'") {
+    CHECK(pow<0>(2m) == 1);
+  }
+
+  SECTION ("'pow<1>(q)' returns 'q'") {
+    CHECK(pow<1>(2m) == 2m);
+  }
+
+  SECTION ("'pow<2>(q)' squares both the value and a dimension") {
+    CHECK(pow<2>(2m) == 4sq_m);
+  }
+
+  SECTION ("'pow<3>(q)' cubes both the value and a dimension") {
+    CHECK(pow<3>(2m) == 8cub_m);
+  }
 }
 
-TEST_CASE("sqrt() on quantity changes the value and the dimension accordingly", "[math][sqrt]")
+TEST_CASE("'sqrt()' on quantity changes the value and the dimension accordingly", "[math][sqrt]")
 {
   REQUIRE(sqrt(4sq_m) == 2m);
 }
-
-// BDD style
-
-SCENARIO("quantities should work with pow<N>()", "[math][pow]")
-{
-  GIVEN("A quantity q") {
-    auto q = 2m;
-
-    REQUIRE(q.count() == 2);
-
-    WHEN("pow<1>(q) is called") {
-      auto res = pow<1>(q);
-
-      THEN("the same quantity is received") {
-        REQUIRE(res == q);
-      }
-    }
-    WHEN("pow<2>(q) is called") {
-      auto res = pow<2>(q);
-
-      THEN("both the value and dimension is raised to the exponent 2") {
-        REQUIRE(res == 4sq_m);
-      }
-    }
-    WHEN("pow<3>(q) is called") {
-      auto res = pow<3>(q);
-
-      THEN("both the value and dimension is raised to the exponent 3") {
-        REQUIRE(res == 8cub_m);
-      }
-    }
-  }
-}
-
-SCENARIO("quantities should work with sqrt()", "[math][sqrt]")
-{
-  GIVEN("A quantity q") {
-    auto q = 4sq_m;
-
-    REQUIRE(q.count() == 4);
-
-    WHEN("sqrt(q) is called") {
-      auto res = sqrt(q);
-
-      THEN("both the value and dimension are square rooted") {
-        REQUIRE(res == 2m);
-      }
-    }
-  }
-}
diff --git a/test/unit_test/static/dimension_op_test.cpp b/test/unit_test/static/dimension_op_test.cpp
index 6f94c6b5..900a8b02 100644
--- a/test/unit_test/static/dimension_op_test.cpp
+++ b/test/unit_test/static/dimension_op_test.cpp
@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/dimension_op.h"
+#include "units/bits/dimension_op.h"
 #include "units/unit.h"
 #include <utility>
 
diff --git a/test/unit_test/static/type_list_test.cpp b/test/unit_test/static/type_list_test.cpp
index 6ee9688f..9c5bec90 100644
--- a/test/unit_test/static/type_list_test.cpp
+++ b/test/unit_test/static/type_list_test.cpp
@@ -20,7 +20,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include "units/bits/type_list.h"
+#include "units/bits/external/type_list.h"
 #include "units/derived_dimension.h"
 #include "units/unit.h"
 #include <utility>
diff --git a/test/unit_test/static/unit_test.cpp b/test/unit_test/static/unit_test.cpp
index a23bee55..84dc5e10 100644
--- a/test/unit_test/static/unit_test.cpp
+++ b/test/unit_test/static/unit_test.cpp
@@ -53,6 +53,6 @@ static_assert(std::is_same_v<downcast<scaled_unit<metre_per_second, ratio_divide
 
 static_assert(centimetre::symbol == "cm");
 static_assert(kilometre::symbol == "km");
-static_assert(kilometre_per_hour::symbol == "");
+static_assert(kilometre_per_hour::symbol == "km/h");
 
 }  // namespace