diff --git a/homeassistant/const.py b/homeassistant/const.py
index 3c0b2a4051c..ad81eb8c692 100644
--- a/homeassistant/const.py
+++ b/homeassistant/const.py
@@ -559,7 +559,10 @@ VOLUME_CUBIC_METERS: Final = "m³"
 VOLUME_CUBIC_FEET: Final = "ft³"
 
 VOLUME_GALLONS: Final = "gal"
+"""US gallon (British gallon is not yet supported)"""
+
 VOLUME_FLUID_OUNCE: Final = "fl. oz."
+"""US fluid ounce (British fluid ounce is not yet supported)"""
 
 # Volume Flow Rate units
 VOLUME_FLOW_RATE_CUBIC_METERS_PER_HOUR: Final = "m³/h"