Gallons to Cubic Feet Calculator — US & Imperial Gallons
Convert any volume in gallons (US liquid or Imperial) to cubic feet, cubic inches, cubic metres and litres. The exact statutory conversion factors are used throughout.
gal
Gallon type
1 US liquid gallon = 0.133681 ft³ (231 in³ ÷ 1728)
0.1337 ft³
- 1
Conversion factor (ft³/gal)
231 ÷ 1728 = 0.1336811 US gal = 231 in³ exactly; 1 ft³ = 1728 in³ exactly. - 2
Volume in cubic feet
1 × 0.133681 = 0.133681
How does this calculator work?
1 US liquid gallon = 0.133681 ft³ (= 231 in³ ÷ 1728). 1 Imperial gallon = 0.160544 ft³. Multiply your gallon count by the relevant factor, or use the calculator to get cubic feet, cubic inches, cubic metres and litres at once. The two gallon types differ by about 20%.
Formula
How this is calculated
The US liquid gallon is defined as exactly 231 cubic inches. Since 1 cubic foot equals exactly 1,728 cubic inches, dividing gives the exact conversion factor: 1 US liquid gallon = 231 ÷ 1,728 = 0.133681 ft³. Running the calculation the other way, 1 cubic foot holds about 7.4805 US gallons.
The Imperial gallon used in the UK, Canada and parts of the Caribbean is defined as exactly 4.54609 litres. Converting to cubic feet requires the litre-to-cubic-foot factor: 1 ft³ = 28.316846592 litres (exact), giving 1 Imperial gallon = 4.54609 ÷ 28.3168 ≈ 0.160544 ft³. The Imperial gallon is about 20% larger than the US gallon, which matters for fuel tank sizing and pool volumes if sources mix the two.
Cubic feet appear in HVAC duct sizing, aquarium volumes, pool and hot-tub capacity, and building material quantities (e.g., ready-mix concrete is sold by the cubic foot). If you know a tank's capacity in gallons and want to verify its physical dimensions, divide cubic feet by height × width to get depth. The Solid3D visualisation shows the equivalent cube whose side equals the cube root of the result.
Frequently asked questions
1 US liquid gallon = 231 cubic inches = 231 ÷ 1728 ≈ 0.13368 cubic feet. Equivalently, 1 cubic foot holds about 7.481 US gallons.
1 Imperial gallon = 4.54609 litres ÷ 28.3168 L/ft³ ≈ 0.16054 cubic feet. One cubic foot holds about 6.229 Imperial gallons. The Imperial gallon is about 20% larger than the US gallon.
Multiply the pool's capacity in US gallons by 0.13368. For example, a 20,000-gallon pool ≈ 20,000 × 0.13368 = 2,673.6 cubic feet. You can verify this against length × width × average depth of the pool in feet.
Also known as
TG we-Calculate Editorial Team. (2026). Gallons to Cubic Feet Calculator — US & Imperial Gallons [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/gallons-to-cubic-feet-calculator
TG we-Calculate Editorial Team. "Gallons to Cubic Feet Calculator — US & Imperial Gallons." TG we-Calculate. 2026. https://we-calculate.com/calculator/gallons-to-cubic-feet-calculator.
TG we-Calculate Editorial Team, "Gallons to Cubic Feet Calculator — US & Imperial Gallons," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/gallons-to-cubic-feet-calculator
@misc{wecalculate_gallons_to_cubic_feet_calculator, title = {Gallons to Cubic Feet Calculator — US & Imperial Gallons}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/gallons-to-cubic-feet-calculator}}, year = {2026}, note = {TG we-Calculate} }
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