Cubic Feet to Gallons Converter
Convert cubic feet to gallons for tanks, aquariums, and pipes. Enter cubic feet and choose US or imperial gallons; the tool also shows liters and cubic inches.
Example: with Cubic feet 1 · Gallon type US gallon → Gallons: 7.4805 US gal.
- In liters28.317 L
- In cubic inches1,728 cu in
Computed by the calculator below using its default values. Change any input to see your own numbers.
1 cubic foot = 28.316846592 L. Divide by the gallon size — 3.785411784 L for US, 4.54609 L for imperial.
Cubic feet to gallons
A cubic foot is a box one foot on each side. It holds 28.317 liters, and since a US gallon is 3.785411784 liters, a cubic foot contains about 7.48 US gallons. That figure is worth memorizing for tanks, aquariums, and water features — multiply cubic feet by roughly 7.5 for a quick US-gallon estimate.
For a tank, find cubic feet first by multiplying length by width by height in feet, then apply the 7.48 factor.
US versus imperial gallons
Gallons come in two sizes. The US gallon is 3.785 liters, so a cubic foot is 7.48 of them. The imperial (UK) gallon is larger at 4.546 liters, so a cubic foot is only about 6.23 imperial gallons. Pick the right one before ordering water treatment or fuel by volume.
The liters figure never changes — only the gallon count does — so when a spec is ambiguous, compare in liters.
How it’s calculated
Liters = cubic feet × 28.316846592. US gallons = liters ÷ 3.785411784 (about 7.4805 per cubic foot). Imperial gallons = liters ÷ 4.54609 (about 6.2288 per cubic foot). Cubic inches = cubic feet × 1728. Factors are NIST values.
Assumes the container is filled to the stated volume; real tanks lose capacity to walls, fittings, and freeboard.
Cubic feet to US gallons and liters
| Cubic feet | US gallons | Liters |
|---|---|---|
| 1 | 7.4805 | 28.317 |
| 5 | 37.403 | 141.584 |
| 10 | 74.805 | 283.168 |
| 20 | 149.610 | 566.337 |
| 50 | 374.026 | 1,415.842 |
1 cubic foot = 28.316846592 L; 1 US gallon = 3.785411784 L (NIST). Imperial gallon = 4.54609 L.
Common mistakes
- Using US gallons when the job needs imperial, or vice versa — they differ by about 20 percent.
- Assuming a filled tank equals its box volume; walls and freeboard cut usable gallons.
- Confusing cubic feet with board feet or square feet.
- Rounding 7.48 too hard on big tanks, where the leftover fraction is many gallons.
Frequently asked questions
How many gallons are in a cubic foot?
About 7.48 US gallons, or 6.23 imperial gallons. Precisely, a cubic foot is 28.316846592 liters divided by the gallon size.
What is the formula for cubic feet to gallons?
Multiply cubic feet by 28.316846592 to get liters, then divide by 3.785411784 for US gallons. The shortcut is cubic feet × 7.4805.
How do I find a tank's gallons from its dimensions?
Multiply length by width by height in feet to get cubic feet, then multiply by 7.48 for US gallons. Subtract a little for wall thickness and the fill line.
Why are US and imperial gallons different?
They are separate historical standards. The US gallon is 3.785 liters and the imperial gallon is 4.546 liters, so the same cubic foot holds fewer imperial gallons.