diff --git a/src/constants.f90 b/src/constants.f90
index 3b99763de..43098188b 100644
--- a/src/constants.f90
+++ b/src/constants.f90
@@ -9,8 +9,8 @@ module constants
   public
 
   real(pReal), parameter :: &
-    T_ROOM = 300.0_pReal, &                                                                         !< Room temperature in K. ToDo: IUPAC: 298.15
-    K_B = 1.38e-23_pReal, &                                                                         !< Boltzmann constant in J/Kelvin
-    N_A = 6.02214076e23_pReal                                                                      !< Avogadro constant in 1/mol
+    T_ROOM = 298.15_pReal, &                                                                        !< Room temperature in K (25°C)/Standard Ambient Temperaure and Pressure (SATP)
+    K_B = 1.380649e-23_pReal, &                                                                     !< Boltzmann constant in J/Kelvin (https://doi.org/10.1351/goldbook)
+    N_A = 6.02214076e23_pReal                                                                       !< Avogadro constant in 1/mol (https://doi.org/10.1351/goldbook)
 
 end module constants