How Much Does a Gallon of Liquid Weigh? Water, Milk & Saltwater

A U.S. liquid gallon is a unit of volume, not a fixed weight. One gallon of fresh water weighs about 8.34 lb (3.78 kg). A gallon of milk is roughly 8.6 lb (3.90 kg) as a practical reference, while a gallon of seawater is about 8.55 lb (3.88 kg) under typical salinity and temperature assumptions. The exact weight changes with density, product composition, and temperature.

These estimates describe the liquid alone. Add the empty jug or container to estimate the total lifted weight. For water-only calculations, see our gallon of water weight chart.

The kilogram values are rounded conversions of the pound estimates. They are useful for planning, not for billing or laboratory measurement.

Use the liquid's density when you need a closer estimate:

weight = volume × density

For household use, weigh a known amount of the liquid or check the product's technical information. Do not assume that every liquid weighs 8.34 lb per gallon: that figure is a freshwater approximation. Chocolate milk and raw milk can vary by recipe, fat content, and solids, so the milk figure above is only a planning estimate. The total for a filled jug also includes the container.

A U.S. liquid gallon is exactly 231 cubic inches, or about 3.785 liters. Weight depends on how much mass fits in that volume. Dissolved salt makes seawater denser than fresh water; temperature and the liquid's ingredients also affect density. A U.S. gallon is different from an Imperial gallon, so confirm the unit before using a conversion.