diff --git a/src/units.h b/src/units.h
index b55548be1642a..adeed5bc33e61 100644
--- a/src/units.h
+++ b/src/units.h
@@ -334,41 +334,54 @@ const mass mass_max = units::mass( std::numeric_limits<units::mass::value_type>:
                                    units::mass::unit_type{} );
 
 template<typename value_type>
-inline constexpr quantity<value_type, mass_in_milligram_tag> from_milligram(
+inline constexpr quantity<value_type, mass_in_microgram_tag> from_microgram(
     const value_type v )
 {
-    return quantity<value_type, mass_in_milligram_tag>( v, mass_in_milligram_tag{} );
+    return quantity<value_type, mass_in_microgram_tag>( v, mass_in_microgram_tag{} );
 }
 
 template<typename value_type>
-inline constexpr quantity<value_type, mass_in_milligram_tag> from_gram(
+inline constexpr quantity<value_type, mass_in_microgram_tag> from_milligram(
+    const value_type v )
+{
+    return from_microgram( v * 1000 );
+}
+
+template<typename value_type>
+inline constexpr quantity<value_type, mass_in_microgram_tag> from_gram(
     const value_type v )
 {
     return from_milligram( v * 1000 );
 }
 
 template<typename value_type>
-inline constexpr quantity<value_type, mass_in_milligram_tag> from_kilogram(
+inline constexpr quantity<value_type, mass_in_microgram_tag> from_kilogram(
     const value_type v )
 {
     return from_gram( v * 1000 );
 }
 
 template<typename value_type>
-inline constexpr value_type to_milligram( const quantity<value_type, mass_in_milligram_tag> &v )
+inline constexpr value_type to_microgram( const quantity<value_type, mass_in_microgram_tag> &v )
 {
     return v.value();
 }
 
 template<typename value_type>
-inline constexpr value_type to_gram( const quantity<value_type, mass_in_milligram_tag> &v )
+inline constexpr value_type to_milligram( const quantity<value_type, mass_in_microgram_tag> &v )
 {
     return v.value() / 1000.0;
 }
 
+template<typename value_type>
+inline constexpr value_type to_gram( const quantity<value_type, mass_in_microgram_tag> &v )
+{
+    return v.value() / 1'000'000.0;
+}
+
 inline constexpr double to_kilogram( const mass &v )
 {
-    return v.value() / 1000000.0;
+    return v.value() / 1'000'000'000.0;
 }
 
 // Specific energy
@@ -783,9 +796,9 @@ inline constexpr quantity<value_type, length_in_millimeter_tag> default_length_f
 // Streaming operators for debugging and tests
 // (for UI output other functions should be used which render in the user's
 // chosen units)
-inline std::ostream &operator<<( std::ostream &o, mass_in_milligram_tag )
+inline std::ostream &operator<<( std::ostream &o, mass_in_microgram_tag )
 {
-    return o << "mg";
+    return o << "μg";
 }
 
 inline std::ostream &operator<<( std::ostream &o, volume_in_milliliter_tag )
@@ -867,7 +880,10 @@ inline constexpr units::quantity<double, units::volume_in_milliliter_tag> operat
     return units::from_milliliter( v * 1000 );
 }
 
-// Implicitly converted to mass, which has int as value_type!
+inline constexpr units::mass operator"" _microgram( const unsigned long long v )
+{
+    return units::from_microgram( v );
+}
 inline constexpr units::mass operator"" _milligram( const unsigned long long v )
 {
     return units::from_milligram( v );
@@ -882,19 +898,24 @@ inline constexpr units::mass operator"" _kilogram( const unsigned long long v )
     return units::from_kilogram( v );
 }
 
-inline constexpr units::quantity<double, units::mass_in_milligram_tag> operator"" _milligram(
+inline constexpr units::quantity<double, units::mass_in_microgram_tag> operator"" _microgram(
+    const long double v )
+{
+    return units::from_microgram( v );
+}
+inline constexpr units::quantity<double, units::mass_in_microgram_tag> operator"" _milligram(
     const long double v )
 {
     return units::from_milligram( v );
 }
 
-inline constexpr units::quantity<double, units::mass_in_milligram_tag> operator"" _gram(
+inline constexpr units::quantity<double, units::mass_in_microgram_tag> operator"" _gram(
     const long double v )
 {
     return units::from_gram( v );
 }
 
-inline constexpr units::quantity<double, units::mass_in_milligram_tag> operator"" _kilogram(
+inline constexpr units::quantity<double, units::mass_in_microgram_tag> operator"" _kilogram(
     const long double v )
 {
     return units::from_kilogram( v );
@@ -1147,6 +1168,8 @@ const std::vector<std::pair<std::string, power>> power_units = { {
     }
 };
 const std::vector<std::pair<std::string, mass>> mass_units = { {
+        { "ug", 1_microgram },
+        { "μg", 1_microgram },
         { "mg", 1_milligram },
         { "g", 1_gram },
         { "kg", 1_kilogram },
diff --git a/src/units_fwd.h b/src/units_fwd.h
index 8a018c3b826e0..e695386fc450e 100644
--- a/src/units_fwd.h
+++ b/src/units_fwd.h
@@ -16,11 +16,11 @@ class volume_in_milliliter_tag
 
 using volume = quantity<int, volume_in_milliliter_tag>;
 
-class mass_in_milligram_tag
+class mass_in_microgram_tag
 {
 };
 
-using mass = quantity<std::int64_t, mass_in_milligram_tag>;
+using mass = quantity<std::int64_t, mass_in_microgram_tag>;
 
 class specific_energy_in_joule_per_gram_tag
 {