Gallons to FT3 Converter
7.48 US gallons = 1 ft³.
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Gallons into cubic feet
Divide by 7.4805 for US gallons. The relationship is exact: 231 cubic inches to the gallon, 1,728 to the cubic foot.
7.4805 US gallons = 1 ft³
The gallon
The two gallons are genuinely different sizes. The US gallon is 3.785411784 litres, defined from the old English wine gallon of 231 cubic inches. The Imperial gallon is 4.54609 litres, defined in 1824 as the volume of ten pounds of water.
The Imperial gallon is about 20 % larger. That difference is why American and British fuel economy figures in miles per gallon cannot be compared without converting first — 30 mpg in Britain is about 25 mpg in America.
The cubic foot
A cube one foot on each side: 28.3168 litres, or 1,728 cubic inches. It is the unit of American gas meters, appliance capacities and shipping volumes.
A cubic foot of fresh water weighs about 62.4 pounds.
The working, step by step
Every line updates with whatever you type above. The point is the method, which is the same for any pair of units in this family.
The same quantity, two different numbers
One physical amount, read off two scales. The tick marks do not line up, and the gap between them is the conversion factor made visible.
How much is that?
A number is easier to judge next to something familiar.
Your turn
Reading a method and being able to use it are different things. Answer within half a per cent and it counts as correct.
Score: 0 of 0
How to use this converter
- Type into either box. The other side updates as you go; there is no button to press.
- Swap the direction with the button between the boxes, carrying your value across.
- Set the decimals if the default is more or less precision than you need.
- Copy the answer with its unit, ready to paste.
- Use the shortcut buttons for the values that come up most often.
- Share the result. The address bar tracks what you type, so the link you copy opens on the same number.
Common uses and tips
Where volume conversions come up
- Cooking from a foreign recipe. The commonest reason, and the one where getting it wrong shows.
- Medicine doses, given in millilitres worldwide and sometimes in teaspoons at home — a genuinely risky place to guess.
- Fuel, where miles per gallon means two different things depending on which side of the Atlantic wrote the figure.
- Engine sizes, quoted in cubic inches, cubic centimetres or litres depending on the market and the decade.
- Building materials such as concrete and topsoil, sold by the cubic yard or cubic metre.
The big one: US and Imperial are different sizes
These are not two names for the same unit. They are different volumes.
- Gallon — US 3.785 L, Imperial 4.546 L. The Imperial one is about 20 % larger.
- Pint — US 473 mL (16 fl oz), Imperial 568 mL (20 fl oz).
- Quart — US 946 mL, Imperial 1,137 mL.
- Fluid ounce — US 29.57 mL, Imperial 28.41 mL. Here the US one is the larger, which catches everyone.
The reason for that last oddity is historical. The US kept the old English wine gallon of 231 cubic inches and divided it into 128 fluid ounces. Britain redefined its gallon in 1824 as ten pounds of water and divided it into 160. More ounces in a bigger gallon means each ounce comes out smaller.
The practical upshot: a British recipe's pint is a fifth more liquid than an American one, and 30 mpg in Britain is about 25 mpg in the United States.
Fluid ounces are not ounces
A fluid ounce measures volume; an ounce measures mass. They are related only for water, where a US fluid ounce weighs about 1.04 oz. For flour, honey or oil the two figures are nowhere near each other, which is why baking by weight is more reliable than baking by cups.
Tips worth knowing
- 1 mL is exactly 1 cm³. Not approximately — exactly, by definition.
- Australian tablespoons are 20 mL, against 15 mL everywhere else. Three tablespoons of an Australian recipe is 60 mL.
- Cubic conversions cube the length factor. A foot is 0.3048 m, so a cubic foot is 0.3048³ = 0.0283 m³.
- Weigh, do not measure, for baking. A cup of flour varies by 20 % depending on how it was packed.
Values people look up most
Each one opens the converter with the number already in it.
Quick reference
Using US gallons.
| Gallons | Cubic feet |
|---|---|
| 1 gal | 0.133681 ft³ |
| 10 gal | 1.336806 ft³ |
| 100 gal | 13.368056 ft³ |
| 1,000 gal | 133.680556 ft³ |
Questions people ask
How many gallons in a cubic foot?
7.4805 US gallons.
Which gallon, pint or cup does this use?
Whichever you pick with the switch above the reference table. US and Imperial measures are genuinely different sizes — an Imperial gallon is about 20 % larger than a US one.