How to convert gallons to pounds
A US gallon of water weighs about 8.345 pounds, so pounds = gallons × 8.345 × density (density relative to water). For 5 gallons of water: 5 × 8.345 = about 41.7 lb. Milk (~1.03) is a little heavier; gasoline (~0.74) is lighter.
Worked example: a 55 gallon drum of diesel at a density of about 0.85 weighs 55 × 8.345 × 0.85 = roughly 390 lb before you count the drum itself. The same drum full of water would come to about 459 lb.
The 8.345 figure comes from a US gallon being 3.785 litres of water at close to one kilogram per litre: 3.785 kg × 2.205 lb per kg = 8.35 lb.
For the same task from a slightly different angle, try the gallons to liters calculator.
The lbs to kg calculator is the natural next step once you have this figure.
How to use this calculator
Enter the gallons and the liquid's density relative to water (1 for water, ~1.03 milk, ~0.74 gasoline). The result is the weight in pounds.
Density here is relative to water, which makes it the same number as specific gravity: 1 for water, about 1.03 for milk, 0.74 for gasoline, 0.85 for diesel and heating oil, 0.92 for olive oil and 1.42 for honey. If your figure is already in kilograms per litre you can use it as it stands, since 0.74 kg/L is a density of 0.74.
Weight matters more than volume once something has to be carried or a shelf loaded: five gallons of water is about 42 lb, which is why a full five gallon jug sits at the limit of what most people lift comfortably.
If you are checking your work, the liters to gallons calculator gives you a second reference point.
Frequently asked questions
- How much does a gallon of water weigh?
- About 8.345 pounds for a US gallon at room temperature.
- How do I convert gallons to pounds?
- Multiply gallons by 8.345 and by the liquid's density relative to water.
- How much do 5 gallons of water weigh?
- About 41.7 pounds.
- Does temperature affect the weight?
- Slightly — water is densest near 4°C and a touch lighter when warm, but 8.345 lb/gal is a good general figure.
- Is a UK imperial gallon the same as a US gallon?
- No. An imperial gallon is 4.546 litres against the US gallon's 3.785, so it holds about 10.02 lb of water rather than 8.345 lb. This calculator uses US gallons, so multiply by 1.201 if your figure is imperial.