US gallons and 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.
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.
Worked example
Convert 100 gal: 100 × 0.1336805556 = 13.36805556, so 100 US gallons is 13.36805556 cubic feet. Likewise 200 gal = 26.73611111 ft³.
Estimating in your head
Divide by 7.5 for a quick figure; it is off by about 0.3%. For 100 gal that gives 13.3 ft³, against 13.3681 exactly.
Going the other way
To convert cubic feet to US gallons, divide by 0.1336805556 (or multiply by 7.48051948052). The swap button between the boxes opens that page.
How this works
ft³ = gal × 0.1336805556
1 gal = 0.003785411784 m³ and 1 ft³ = 0.028316846592 m³, both by definition, so the factor is their ratio: 0.1336805556 (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 cubic feet are in a US gallon?
1 US gallon = 0.1336805556 cubic feet. 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 US gallons to cubic feet?
Multiply by 0.1336805556. For example, 200 gal × 0.1336805556 = 26.73611111 ft³.
What is 1,000 gal in cubic feet?
1,000 gal = 133.6805556 ft³. 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/gallons-to-cubic-feet/