diff --git a/homeassistant/const.py b/homeassistant/const.py
index 02b4681f3d8..dfdab178d76 100644
--- a/homeassistant/const.py
+++ b/homeassistant/const.py
@@ -767,6 +767,7 @@ class UnitOfMass(StrEnum):
     MICROGRAMS = "µg"
     OUNCES = "oz"
     POUNDS = "lb"
+    STONES = "st"
 
 
 MASS_GRAMS: Final = "g"
diff --git a/homeassistant/util/unit_conversion.py b/homeassistant/util/unit_conversion.py
index 70d2474fd95..a1c41172ed9 100644
--- a/homeassistant/util/unit_conversion.py
+++ b/homeassistant/util/unit_conversion.py
@@ -33,7 +33,8 @@ _DAYS_TO_SECS = 24 * _HRS_TO_SECS  # 1 day = 24 hours = 86400 seconds
 
 # Mass conversion constants
 _POUND_TO_G = 453.59237
-_OUNCE_TO_G = _POUND_TO_G / 16
+_OUNCE_TO_G = _POUND_TO_G / 16  # 16 ounces to a pound
+_STONE_TO_G = _POUND_TO_G * 14  # 14 pounds to a stone
 
 # Pressure conversion constants
 _STANDARD_GRAVITY = 9.80665
@@ -143,6 +144,7 @@ class MassConverter(BaseUnitConverter):
         UnitOfMass.KILOGRAMS: 1 / 1000,
         UnitOfMass.OUNCES: 1 / _OUNCE_TO_G,
         UnitOfMass.POUNDS: 1 / _POUND_TO_G,
+        UnitOfMass.STONES: 1 / _STONE_TO_G,
     }
     VALID_UNITS = {
         UnitOfMass.GRAMS,
@@ -151,6 +153,7 @@ class MassConverter(BaseUnitConverter):
         UnitOfMass.MICROGRAMS,
         UnitOfMass.OUNCES,
         UnitOfMass.POUNDS,
+        UnitOfMass.STONES,
     }
 
 
diff --git a/tests/util/test_unit_conversion.py b/tests/util/test_unit_conversion.py
index b2b99d6f8c0..fdd187905d3 100644
--- a/tests/util/test_unit_conversion.py
+++ b/tests/util/test_unit_conversion.py
@@ -345,6 +345,11 @@ def test_energy_convert(
         (16, UnitOfMass.OUNCES, 453592.37, UnitOfMass.MILLIGRAMS),
         (16, UnitOfMass.OUNCES, 453592370, UnitOfMass.MICROGRAMS),
         (16, UnitOfMass.OUNCES, 1, UnitOfMass.POUNDS),
+        (1, UnitOfMass.STONES, pytest.approx(6.350293), UnitOfMass.KILOGRAMS),
+        (1, UnitOfMass.STONES, pytest.approx(6350.293), UnitOfMass.GRAMS),
+        (1, UnitOfMass.STONES, pytest.approx(6350293), UnitOfMass.MILLIGRAMS),
+        (1, UnitOfMass.STONES, pytest.approx(14), UnitOfMass.POUNDS),
+        (1, UnitOfMass.STONES, pytest.approx(224), UnitOfMass.OUNCES),
     ],
 )
 def test_mass_convert(