Gallons to PoundsHow much does a gallon of water weigh?
One US gallon of water at 70°F (21°C) weighs about 8.33 pounds, or 3.78 kilograms. Five US gallons at that temperature weigh about 41.64 pounds. Those figures count the water alone. The bottle, bucket or tank adds its own weight.
A gallon is a volume, so its weight depends on what fills it. This page uses water densities for the temperatures in the menu. For milk, oil, fuel or another liquid, use the gallons to pounds converter and select a suitable density.
Water weight chart for common amounts
This chart uses US liquid gallons and the USGS density of 0.99802 kg/L at 70°F. These are calculated values rounded to two decimals, with no container included.
| US gallons | Pounds | Kilograms |
|---|---|---|
| 1 | 8.33 | 3.78 |
| 5 | 41.64 | 18.89 |
| 10 | 83.29 | 37.78 |
| 20 | 166.58 | 75.56 |
| 55 | 458.09 | 207.78 |
| 100 | 832.89 | 377.79 |
US and Imperial gallons give different answers
A US liquid gallon is 3.785411784 liters. An Imperial gallon is 4.54609 liters. The Imperial gallon holds about 20.1% more water, so it also weighs about 20.1% more at the same temperature. At 70°F, one Imperial gallon of water weighs about 10.00 pounds.
The calculator starts with US gallons for the common US use case. Change the volume unit if your measurement or product label uses Imperial gallons. For a volume already in liters, enter liters directly rather than rounding it into gallons first.
Why temperature matters
The density of water changes with temperature and dissolved substances. This calculator uses entries from the USGS water density table directly. It does not treat the density as exactly 1 kg/L at every temperature, and it does not estimate a value between listed temperatures.
The difference is small for a single household container, but grows with the volume. At the listed 39.2°F density, 100 US gallons weigh about 834.54 pounds. At 100°F, the same measured volume weighs about 828.85 pounds. Salt water, concentrated solutions and ice need different density assumptions; this water-only menu is not a model for those materials.
Add the empty container once
The optional container field separates two useful answers: the weight of the water and the weight of the filled container. Enter a measured or specified empty weight. Leaving it blank adds zero and makes both answers the same.
For example, five US gallons of water at 70°F weigh about 41.64 pounds. If your empty container weighs 2 pounds, the combined weight is about 43.64 pounds. The 2-pound value is an illustration, not a standard bucket weight.
For several containers, either enter their combined empty weight with the combined water volume or calculate each container separately. Do not add an empty weight to a scale reading that already includes the container. For a partly filled tank, use the water actually inside it, not the full nominal tank size.
The formula behind the result
Water weight in lb = water mass in kg ÷ 0.45359237
Combined weight = water weight + empty container weight
The calculator retains precision until it displays the answer. Extra decimal places do not make a container’s marked volume more accurate. The combined result is a weight estimate; it does not determine whether a shelf, floor or vehicle can support that load.
Sources and privacy
Density values: USGS Water Science School, Water Density. Unit definitions: NIST Guide to the SI and NIST Handbook 44, Appendix C (US gallon: 231 cubic inches). Checked September 14, 2026. Calculations run on your device; this page does not save its inputs.
For a reverse weight-to-volume calculation, multiple liquids or a batch of amounts, open the main converter. Send a correction or a practical suggestion to contact@gallonstopounds.org.