Cubic feet and US gallons
The cubic foot is a cube 1 foot on each side: exactly 28.316846592 liters. Refrigerators, storage units, gas meters and air flow (CFM) in the US are measured in cubic feet.
The US liquid gallon is defined as exactly 231 cubic inches, which is 3.785411784 liters. Gasoline, milk and paint are sold by the gallon in the US.
Worked example
Convert 10 ft³: 10 × 7.480519481 = 74.80519481, so 10 cubic feet is 74.80519481 US gallons. Likewise 50 ft³ = 374.025974 gal.
Estimating in your head
Multiply by 7.5 for a quick figure; it is off by about 0.3%. For 10 ft³ that gives 75 gal, against 74.8052 exactly.
Going the other way
To convert US gallons to cubic feet, divide by 7.480519481 (or multiply by 0.133680555556). The swap button between the boxes opens that page.
How this works
gal = ft³ × 7.480519481
1 ft³ = 0.028316846592 m³ and 1 gal = 0.003785411784 m³, both by definition, so the factor is their ratio: 7.480519481 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many US gallons are in a cubic foot?
1 cubic foot = 7.480519481 US gallons. The factor is exact by definition but has endless decimals, so it is shown rounded; the page uses the full value.
How do I convert cubic feet to US gallons?
Multiply by 7.480519481. For example, 50 ft³ × 7.480519481 = 374.025974 gal.
What is 100 ft³ in US gallons?
100 ft³ = 748.0519481 gal. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- NIST Handbook 44 — Appendix C, General tables of units of measurement
- Wikipedia — United States customary units
Reviewed Oct 17, 2026 · test vectors fixtures/units/volume/cubic-feet-to-gallons/