Twenty US gallons of fresh water weighs about 167 pounds, or roughly 75.6 kilograms, at room temperature.
For the full breakdown, see our best 20 Gallon Water Container guide.
If you’re hauling a filled 20-gallon container from the store to your truck, that number is the one that matters. The math behind it is simple, but two factors can shift the total: water temperature and which gallon you’re actually using. Here’s what the weight really comes down to and why the difference matters.
The Straightforward Calculation
Water is commonly treated as weighing 8.34 pounds per US gallon in everyday planning. Multiply that by 20, and you get 166.8 pounds. Round it up and you have your practical answer: about 167 pounds.
Some sources use the slightly lower figure of 8.33 pounds per gallon, which gives 166.6 pounds. NIST’s water-density tables show the exact value depends on temperature, so both numbers are defensible. The safe, simple statement for planning is that 20 US gallons weighs about 167 pounds at room temperature.
Plan for 167 pounds as your working number. If you’re loading a truck bed or a cart, assume the total could edge slightly higher.
Why Temperature Changes the Number
Water is densest near 39.2°F (4°C), and its density drops as it warms. Cold water packs more mass into the same volume, so 20 gallons of cold water weighs a touch more than 20 gallons of warm water. The difference is small — typically a fraction of a pound — but it exists. NIST’s published density tables document this variation across temperatures.
For household or emergency-use planning, the temperature swing rarely matters. For precise industrial or scientific work, it does.
US Gallons vs. Imperial Gallons
This weight applies specifically to the US liquid gallon. The imperial gallon used in the UK and some Commonwealth countries is larger, so 20 imperial gallons is a different volume and a heavier load. If you aren’t sure which gallon your container is marked in, check the label before you assume a weight.
For a 20-gallon water container, you’re likely looking at a US measure, but the distinction is worth confirming when the number matters.
When You’re Moving That Much Water
If you’re filling and hauling a large container, plan your route before you lift. A full 20-gallon container demands two people, a dolly, or a truck-bed placement that avoids a heavy lift. Salt water or treated water will weigh more than fresh, so adjust if you’re working with something other than plain tap water.
If you’re in the market for a container that can handle that load, our roundup of 20 gallon water container options covers the tested picks worth considering.
NIST’s water-density tables from its circular on the properties of water remain the authoritative reference for the density values behind these calculations.
| Calculation Basis | Weight per US Gallon | Total for 20 Gallons |
|---|---|---|
| Common rule of thumb | 8.34 lb | 166.8 lb |
| Alternate common value | 8.33 lb | 166.6 lb |
| Room-temperature estimate | ~8.34 lb | ~167 lb (75.6 kg) |
The 167-pound figure handles every practical scenario you’ll face at home. Load for 167, and you won’t be surprised.
FAQs
Does the weight change if the water is cold or hot?
Yes, slightly. Water is densest near 39.2°F and expands as it warms, so cold water weighs a bit more per gallon than hot water. For 20 gallons, the difference is usually under a pound, so it rarely matters for everyday tasks like filling a storage container.
Is 20 imperial gallons the same weight as 20 US gallons?
No. An imperial gallon is about 20% larger than a US gallon, so 20 imperial gallons weighs considerably more than 167 pounds. Always check which gallon standard your container uses, especially if it was manufactured outside the United States.
Does salt water weigh more than fresh water?
Yes, salt water is denser than fresh water, so the same 20-gallon volume weighs more when it contains dissolved salts. For planning purposes, assume a slightly higher total if you’re working with seawater or brine rather than tap water.
References & Sources
- NIST. “Circular of the Bureau of Standards No. 19: The Properties of Water.” Documents water density variation across temperatures.
