Pounds to Gallons

A pound does not become gallons on its own

A pound measures weight, a gallon measures volume, and density is what converts one into the other. The lighter the substance, the more gallons the same pounds fill: ten pounds of water is 1.2 gallons, ten pounds of vegetable oil 1.3 gallons, and ten pounds of liquid propane 2.36 gallons. When no substance is named, this calculator answers for water and shows the rest in a table.

Both constants are exact by definition: the international pound is exactly 0.45359237 kilograms, and the US liquid gallon — 231 cubic inches — is exactly 3.785411784 liters. Put simply, divide the pounds by the weight of one gallon of that substance.

Three steps

1. Find what one gallon weighs — in the table below. For water that is 8.33 lbs.
2. Divide the pounds by it. Thirty pounds of water is 3.6 gallons — division rarely comes out even, so the figure is rounded.
3. Check which gallon you need. The answer is in US gallons; in imperial gallons, which are about a fifth larger, the same thirty pounds of water is 3 gallons.

How many gallons one pound and five pounds fill

If the substance is not known in advance, start from how many gallons 35 lbs is — water first, then every other liquid at the same weight. The opposite question, what a number of gallons weighs, is on the gallons to pounds page.

Where this actually comes up

• Propane tanks. Tanks are sold by the pounds of gas they hold: a 100-lb tank carries 23.6 gallons of liquid propane, a 20-lb grill cylinder 4.72 gallons.
• Fryer oil. Cooking oil for restaurants comes in 35-lb jugs, which hold 4.56 gallons.
• Payload limits. A trailer or an RV rated for a given weight of water tells you how big a tank it can carry: 500 lbs of water is 60 gallons.
• Dairy. Milk is weighed at the farm and sold by the gallon: 100 lbs of milk is 11.6 gallons.
• Shipping and storage. A delivery note in pounds has to be turned into gallons to know whether the drums or the tank will hold it.

Where the pound and the gallon come from

The pound used here is the international avoirdupois pound, fixed in 1959 at exactly 0.45359237 kilograms by agreement between the United States and the Commonwealth. The US gallon is the old English wine gallon of 231 cubic inches, kept by the United States after Britain replaced its gallons in 1824 with the larger imperial gallon — defined then as the volume of ten pounds of water, which is why a UK gallon of water still weighs close to ten pounds.

Doing it in your head

For water, divide the pounds by eight and take off a bit: a gallon of water is 8.33 lbs, so 80 lbs is a little under ten gallons — the full calculation gives 9.61 gallons. Milk is almost the same (8.6 lbs a gallon); vegetable oil is closer to seven and three quarters (7.68 lbs); propane is about four (4.24 lbs), so divide by four and take off a little.

Where the densities come from

The densities are shared with the kilograms to liters and liters to kilograms pages, and every figure carries a citable source: the FAO/INFOODS density database for food liquids, ISO 3993 for propane. Water is taken at 20 °C (68 °F). The same question in liters is on the pounds to liters page.