diff --git a/src/physical_constants.c b/src/physical_constants.c
index a582f1724041727d4c85ebf360bdc382fa9e962e..bbd8672d530e0ff672273b6c28de796bfa1baebe 100644
--- a/src/physical_constants.c
+++ b/src/physical_constants.c
@@ -125,6 +125,12 @@ void phys_const_init(const struct unit_system *us, struct swift_params *params,
   internal_const->const_light_year =
       const_light_year_cgs /
       units_general_cgs_conversion_factor(us, dimension_length);
+  internal_const->const_solar_radius =
+      const_solar_radius_cgs /
+      units_general_cgs_conversion_factor(us, dimension_length);
+  internal_const->const_earth_radius =
+      const_earth_radius_cgs /
+      units_general_cgs_conversion_factor(us, dimension_length);
 
   const float dimension_power[5] = {1, 2, -3, 0, 0}; /* [g cm^2 s^-3] */
   internal_const->const_solar_luminosity =
@@ -169,9 +175,10 @@ void phys_const_print(const struct phys_const *internal_const) {
   message("%25s = %e", "Electron-Volt", internal_const->const_electron_volt);
   message("%25s = %e", "Proton mass", internal_const->const_proton_mass);
   message("%25s = %e", "Year", internal_const->const_year);
+  message("%25s = %e", "Parsec", internal_const->const_parsec);
   message("%25s = %e", "Astronomical Unit",
           internal_const->const_astronomical_unit);
-  message("%25s = %e", "Parsec", internal_const->const_parsec);
+  message("%25s = %e", "Earth radius", internal_const->const_earth_radius);
   message("%25s = %e", "Solar mass", internal_const->const_solar_mass);
   message("%25s = %e", "Solar luminosity",
           internal_const->const_solar_luminosity);
@@ -226,6 +233,8 @@ void phys_const_print_snapshot(hid_t h_file, const struct phys_const *p) {
                        const_astronomical_unit_cgs);
   io_write_attribute_d(h_grp_cgs, "parsec", const_parsec_cgs);
   io_write_attribute_d(h_grp_cgs, "light_year", const_light_year_cgs);
+  io_write_attribute_d(h_grp_cgs, "solar_radius", const_solar_radius_cgs);
+  io_write_attribute_d(h_grp_cgs, "earth_radius", const_earth_radius_cgs);
   io_write_attribute_d(h_grp_cgs, "solar_mass", const_solar_mass_cgs);
   io_write_attribute_d(h_grp_cgs, "earth_mass", const_earth_mass_cgs);
   io_write_attribute_d(h_grp_cgs, "solar_luminosity",
@@ -262,6 +271,8 @@ void phys_const_print_snapshot(hid_t h_file, const struct phys_const *p) {
                        p->const_astronomical_unit);
   io_write_attribute_d(h_grp_int, "parsec", p->const_parsec);
   io_write_attribute_d(h_grp_int, "light_year", p->const_light_year);
+  io_write_attribute_d(h_grp_int, "solar_radius", p->const_solar_radius);
+  io_write_attribute_d(h_grp_int, "earth_radius", p->const_earth_radius);
   io_write_attribute_d(h_grp_int, "solar_mass", p->const_solar_mass);
   io_write_attribute_d(h_grp_int, "earth_mass", p->const_earth_mass);
   io_write_attribute_d(h_grp_cgs, "solar_luminosity",
diff --git a/src/physical_constants.h b/src/physical_constants.h
index 8469b22e9eb3fa5c632423aa308f1a122fd9d69d..db034875fcc11d999ad3a50003ff9f220133cec8 100644
--- a/src/physical_constants.h
+++ b/src/physical_constants.h
@@ -91,6 +91,12 @@ struct phys_const {
   /*! Mass of the Earth */
   double const_earth_mass;
 
+  /*! Radius of the Sun */
+  double const_solar_radius;
+
+  /*! Radius of the Earth */
+  double const_earth_radius;
+
   /*! Luminosity of the Sun */
   double const_solar_luminosity;
 
diff --git a/src/physical_constants_cgs.h b/src/physical_constants_cgs.h
index f72dc80d16653ff01816c922dbe98f4df41dbe90..0a12240165985bea2c69071746dda2ea212576ad 100644
--- a/src/physical_constants_cgs.h
+++ b/src/physical_constants_cgs.h
@@ -109,6 +109,12 @@ const double const_parsec_cgs = 3.08567758149e18;
 /*! Light-year [cm] */
 const double const_light_year_cgs = 9.46063e17;
 
+/*! Solar radius [cm] */
+const double const_solar_radius_cgs = 6.957e10;
+
+/*! Earth radius [cm] */
+const double const_earth_radius_cgs = 6.3781e8;
+
 #ifdef SWIFT_USE_GADGET2_PHYSICAL_CONSTANTS
 
 /*! Mass of the Sun [g] */