diff --git a/src/include/units/physical/iau/length.h b/src/include/units/physical/iau/length.h
index fd7a92b7..f7acbd76 100644
--- a/src/include/units/physical/iau/length.h
+++ b/src/include/units/physical/iau/length.h
@@ -27,9 +27,14 @@
 
 namespace units::iau {
 
-struct light_year : named_scaled_unit<light_year,"ly",no_prefix,ratio<946073,100000,15>,si::metre> {};
-struct parsec : named_scaled_unit<parsec,"pc",no_prefix,ratio<1542839,500000,16>,si::metre> {};
-struct angstrom : named_scaled_unit<angstrom,"angstrom",no_prefix,ratio<1,1,-10>,si::metre> {};
+// https://en.wikipedia.org/wiki/Light-year
+struct light_year : named_scaled_unit<light_year, "ly", no_prefix, ratio<9460730472580800>, si::metre> {};
+
+// https://en.wikipedia.org/wiki/Parsec
+struct parsec : named_scaled_unit<parsec, "pc", si::prefix, ratio<30'856'775'814'913'673>, si::metre> {};
+
+// https://en.wikipedia.org/wiki/Angstrom
+struct angstrom : named_scaled_unit<angstrom, "angstrom", no_prefix, ratio<1, 1, -10>, si::metre> {};
 
 inline namespace literals {
 
diff --git a/src/include/units/physical/imperial/length.h b/src/include/units/physical/imperial/length.h
index 4ece6b44..3e049898 100644
--- a/src/include/units/physical/imperial/length.h
+++ b/src/include/units/physical/imperial/length.h
@@ -22,12 +22,15 @@
 
 #pragma once
 
-#include <units/physical/si/length.h>
+#include <units/physical/international/length.h>
 
 namespace units::imperial {
 
-struct chain : named_scaled_unit<chain,"ch",no_prefix,ratio<502921,250000,1>, si::metre> {};
-struct rod : named_scaled_unit<rod,"rd",no_prefix, ratio<502921,100000>,si::metre> {};
+// https://en.wikipedia.org/wiki/Chain_(unit)
+struct chain : named_scaled_unit<chain, "ch", no_prefix, ratio<22, 1>, international::yard> {};
+
+// https://en.wikipedia.org/wiki/Rod_(unit)
+struct rod : named_scaled_unit<rod, "rd", no_prefix, ratio<1, 4>, chain> {};
 
 inline namespace literals {
 
@@ -37,7 +40,6 @@ constexpr auto operator"" ch(long double l) { return si::length<chain, long doub
 constexpr auto operator"" rd(unsigned long long l) { return si::length<rod, std::int64_t>(l); }
 constexpr auto operator"" rd(long double l) { return si::length<rod, long double>(l); }
 
-
 }  // namespace literals
 
-}  // namespace units::si
+}  // namespace units::imperial
diff --git a/src/include/units/physical/international/length.h b/src/include/units/physical/international/length.h
index 328ac9f6..adf6b984 100644
--- a/src/include/units/physical/international/length.h
+++ b/src/include/units/physical/international/length.h
@@ -25,41 +25,38 @@
 
 #include <units/physical/si/length.h>
 
-/*
- international units of length are defined in terms of the si metre
-*/
-
 namespace units::international {
 
-//international yard
-//https://en.wikipedia.org/wiki/International_yard_and_pound
-struct yard : named_scaled_unit<yard, "yd", no_prefix, ratio<9'144, 1'000,-1>, si::metre> {};
+// international yard
+// https://en.wikipedia.org/wiki/International_yard_and_pound
+struct yard : named_scaled_unit<yard, "yd", no_prefix, ratio<9'144, 1'000, -1>, si::metre> {};
 
-//international foot
-//https://en.wikipedia.org/wiki/Foot_(unit)#International_foot
-struct foot : named_scaled_unit<foot, "ft", no_prefix, ratio<3'048,1'000,-1>, si::metre> {};
+// international foot
+// https://en.wikipedia.org/wiki/Foot_(unit)#International_foot
+struct foot : named_scaled_unit<foot, "ft", no_prefix, ratio<1, 3>, yard> {};
 
-//https://en.wikipedia.org/wiki/Fathom#International_fathom
-struct fathom : named_scaled_unit<fathom, "fathom",no_prefix,ratio<1'828,1'000>,si::metre > {};
+// https://en.wikipedia.org/wiki/Fathom#International_fathom
+struct fathom : named_scaled_unit<fathom, "fathom", no_prefix, ratio<2>, yard> {};
 
-//international inch
-//https://en.wikipedia.org/wiki/Inch#Equivalences
-struct inch : named_scaled_unit<inch, "in", no_prefix, ratio<254,100,-2>, si::metre> {};
+// international inch
+// https://en.wikipedia.org/wiki/Inch#Equivalences
+struct inch : named_scaled_unit<inch, "in", no_prefix, ratio<1, 36>, yard> {};
 
-//intrnational mile
-//https://en.wikipedia.org/wiki/Mile#International_mile
-struct mile : named_scaled_unit<mile, "mi", no_prefix, ratio<25'146,15'625,3>, si::metre> {};
+// intrnational mile
+// https://en.wikipedia.org/wiki/Mile#International_mile
+struct mile : named_scaled_unit<mile, "mi", no_prefix, ratio<25'146, 15'625>, si::kilometre> {};
 
-//international nautical mile
-//https://en.wikipedia.org/wiki/Mile#Nautical_mile
-struct nautical_mile : named_scaled_unit<nautical_mile,"mi(naut)",no_prefix, ratio<463,250,3>,si::metre> {};
+// international nautical mile
+// https://en.wikipedia.org/wiki/Nautical_mile
+struct nautical_mile : named_scaled_unit<nautical_mile, "mi(naut)", no_prefix, ratio<1852>, si::metre> {};
 
-//TODO thou
-//https://en.wikipedia.org/wiki/Thousandth_of_an_inch
-//struct thou : named_scaled_unit<thou,"thou",no_prefix,ratio<127,50,-5>,si::metre> {};
-// different name for thou
-//https://en.wikipedia.org/wiki/Thousandth_of_an_inch
-struct mil : named_scaled_unit<mil,"mil",no_prefix,ratio<127,50,-5>,si::metre> {};
+// thou
+// https://en.wikipedia.org/wiki/Thousandth_of_an_inch
+struct thou : named_scaled_unit<thou, "thou", no_prefix, ratio<1, 1000>, inch> {};
+
+// mil - different name for thou
+// https://en.wikipedia.org/wiki/Thousandth_of_an_inch
+using mil = thou;
 
 inline namespace literals {
 
@@ -87,14 +84,14 @@ constexpr auto operator"" mi(long double l) { return si::length<mile, long doubl
 constexpr auto operator"" naut_mi(unsigned long long l) { return si::length<nautical_mile, std::int64_t>(l); }
 constexpr auto operator"" naut_mi(long double l) { return si::length<nautical_mile, long double>(l); }
 
-//TODO thou
-//constexpr auto operator"" thou(unsigned long long l) { return si::length<thou, std::int64_t>(l); }
-//constexpr auto operator"" thou(long double l) { return si::length<thou, long double>(l); }
+// thou
+constexpr auto operator"" thou(unsigned long long l) { return si::length<thou, std::int64_t>(l); }
+constexpr auto operator"" thou(long double l) { return si::length<thou, long double>(l); }
 
 // mil
 constexpr auto operator"" mil(unsigned long long l) { return si::length<mil, std::int64_t>(l); }
 constexpr auto operator"" mil(long double l) { return si::length<mil, long double>(l); }
 
-} // namespace literals
+}  // namespace literals
 
-} //namespace units::international
\ No newline at end of file
+}  // namespace units::international
diff --git a/src/include/units/physical/si/density.h b/src/include/units/physical/si/density.h
index d82aada4..1686f2c5 100644
--- a/src/include/units/physical/si/density.h
+++ b/src/include/units/physical/si/density.h
@@ -32,7 +32,7 @@ namespace units::si {
 
 struct kilogram_per_metre_cub : unit<kilogram_per_metre_cub> {};
 
-struct dim_density : physical::dim_density<dim_density, kilogram_per_metre_cub,dim_mass, dim_length> {};
+struct dim_density : physical::dim_density<dim_density, kilogram_per_metre_cub, dim_mass, dim_length> {};
 
 template<Unit U, Scalar Rep = double>
 using density = quantity<dim_density, U, Rep>;
diff --git a/src/include/units/physical/si/length.h b/src/include/units/physical/si/length.h
index 53c225f1..49b3c7e3 100644
--- a/src/include/units/physical/si/length.h
+++ b/src/include/units/physical/si/length.h
@@ -34,7 +34,7 @@ struct centimetre : prefixed_unit<centimetre, centi, metre> {};
 struct decimetre : prefixed_unit<decimetre, deci, metre> {};
 struct hectometre : prefixed_unit<hectometre, hecto, metre> {};
 struct kilometre : prefixed_unit<kilometre, kilo, metre> {};
-struct femtometre : prefixed_unit<femtometre,femto,metre> {};
+struct femtometre : prefixed_unit<femtometre, femto, metre> {};
 
 struct astronomical_unit : named_scaled_unit<astronomical_unit, "au", no_prefix, ratio<149'597'870'700>, metre> {};
 
diff --git a/src/include/units/physical/typographic/length.h b/src/include/units/physical/typographic/length.h
index 2b1cfe12..1584b174 100644
--- a/src/include/units/physical/typographic/length.h
+++ b/src/include/units/physical/typographic/length.h
@@ -27,26 +27,27 @@
 
 namespace units::typographic {
 
-struct pica_comp : named_scaled_unit<pica_comp,"pica(comp)",no_prefix,ratio<4233333,1000000,-3>,si::metre> {};
-struct pica_prn : named_scaled_unit<pica_prn,"pica(prn)",no_prefix,ratio<2108759,500000,-3>,si::metre> {};
-struct point_comp : named_scaled_unit<point_comp,"point(comp)",no_prefix,ratio<1763889,500000,-4>,si::metre> {};
-struct point_prn  : named_scaled_unit<point_prn,"point(prn)", no_prefix, ratio<1757299,500000,-4>,si::metre> {};
+// TODO Conflicts with (https://en.wikipedia.org/wiki/Pica_(typography)), verify correctness of below conversion factors and provide hyperlinks to definitions
+struct pica_comp : named_scaled_unit<pica_comp, "pica(comp)", no_prefix, ratio<4233333, 1000000, -3>, si::metre> {};
+struct pica_prn : named_scaled_unit<pica_prn, "pica(prn)", no_prefix, ratio<2108759, 500000, -3>, si::metre> {};
+struct point_comp : named_scaled_unit<point_comp, "point(comp)", no_prefix, ratio<1763889, 500000, -4>, si::metre> {};
+struct point_prn : named_scaled_unit<point_prn, "point(prn)", no_prefix, ratio<1757299, 500000, -4>, si::metre> {};
 
 inline namespace literals {
 
-  // pica comp
+// pica comp
 constexpr auto operator"" pica_comp(unsigned long long l) { return si::length<pica_comp, std::int64_t>(l); }
 constexpr auto operator"" pica_comp(long double l) { return si::length<pica_comp, long double>(l); }
 
-  // pica prn
+// pica prn
 constexpr auto operator"" pica_prn(unsigned long long l) { return si::length<pica_prn, std::int64_t>(l); }
 constexpr auto operator"" pica_prn(long double l) { return si::length<pica_prn, long double>(l); }
 
-  // point comp
+// point comp
 constexpr auto operator"" point_comp(unsigned long long l) { return si::length<point_comp, std::int64_t>(l); }
 constexpr auto operator"" point_comp(long double l) { return si::length<point_comp, long double>(l); }
 
-  // point prn
+// point prn
 constexpr auto operator"" point_prn(unsigned long long l) { return si::length<point_prn, std::int64_t>(l); }
 constexpr auto operator"" point_prn(long double l) { return si::length<point_prn, long double>(l); }
 
diff --git a/src/include/units/physical/us/length.h b/src/include/units/physical/us/length.h
index 1abd9f75..14c468c9 100644
--- a/src/include/units/physical/us/length.h
+++ b/src/include/units/physical/us/length.h
@@ -26,19 +26,16 @@
 
 namespace units::us {
 
-//https://en.wikipedia.org/wiki/Foot_(unit)#US_survey_foot
-//https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
-//struct foot : named_scaled_unit<foot,"ft(us)",no_prefix,ratio<3'048,1'000,-1>, si::metre> {};
-//################### causes integer overflow when converting for volume #######################
-struct foot : named_scaled_unit<foot,"ft(us)",no_prefix,ratio<1'524'003,5,-6>, si::metre> {};
-//#############################################################################################
+// https://en.wikipedia.org/wiki/Foot_(unit)#US_survey_foot
+// https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
+struct foot : named_scaled_unit<foot, "ft(us)", no_prefix, ratio<1'200, 3'937>, si::metre> {};
 
-//https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
-struct fathom : named_scaled_unit<fathom,"fathom(us)",no_prefix,ratio<6,1>,us::foot> {};
+// https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
+struct fathom : named_scaled_unit<fathom, "fathom(us)", no_prefix, ratio<6>, foot> {};
 
-//https://en.wikipedia.org/wiki/Mile#U.S._survey_mile
-//https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
-struct mile : named_scaled_unit<mile,"mi(us)",no_prefix,ratio<5280,1000,3>,us::foot> {};
+// https://en.wikipedia.org/wiki/Mile#U.S._survey_mile
+// https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors#B6
+struct mile : named_scaled_unit<mile, "mi(us)", no_prefix, ratio<5280>, us::foot> {};
 
 inline namespace literals {