diff --git a/src/include/units/physical/si/constants.h b/src/include/units/physical/si/constants.h
new file mode 100644
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+++ b/src/include/units/physical/si/constants.h
@@ -0,0 +1,45 @@
+// 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/constant.h>
+#include <units/physical/si/electric_charge.h>
+#include <units/physical/si/frequency.h>
+#include <units/physical/si/energy.h>
+#include <units/physical/si/power.h>
+#include <units/physical/si/substance.h>
+#include <units/physical/si/velocity.h>
+#include <units/physical/si/temperature.h>
+
+namespace units::si {
+
+inline constexpr auto planck_constant = constant<ratio<662607015, 1, -42>, exp<dim_energy, 1>, exp<dim_time, 1>>;
+inline constexpr auto elementary_charge = constant<ratio<1602176634, 1, -51>, exp<dim_electric_charge, 1>>;
+inline constexpr auto boltzmann_constant =
+    constant<ratio<1380649, 1, -29>, exp<dim_energy, 1>, exp<dim_thermodynamic_temperature, -1>>;
+inline constexpr auto avogadro_constant = constant<ratio<602214076, 1, 15>, exp<dim_substance, -1>>;
+inline constexpr auto speed_of_light = constant<ratio<299792458, 1, 15>, exp<dim_velocity, 1>>;
+inline constexpr auto hyperfine_structure_transition_frequency = constant<ratio<9192631770>, exp<dim_frequency, 1>>;
+// inline constexpr auto luminous_efficacy = constant<ratio<683>, exp<luminous_flux, 1>, exp<power, -1>>;
+
+}  // namespace units::si