Cubic Feet to Gallons Calculator
Convert cubic feet to US gallons, Imperial gallons or liters. Pick the input unit and watch all three outputs update instantly.
Conversion Factors
1 ft³ = 7.48052 US gallons
1 ft³ = 6.22884 Imperial gallons
1 ft³ = 28.3168 liters
US and Imperial gallons differ: 1 US gallon = 3.785 L, while 1 Imperial gallon (UK) = 4.546 L — about 20% larger.
Common Applications
Aquariums
Aquarium capacity is rated in gallons. Measure the inside dimensions, calculate cubic feet (L × W × H in feet), multiply by 7.48. A 30 × 12 × 12 in tank = 4,320 in³ ÷ 1,728 = 2.5 ft³ × 7.48 = 18.7 gallons.
Tanks and Water Storage
Cylindrical or rectangular tanks: calculate cubic feet, multiply by 7.48 for usable US gallons. Always subtract 5–10% for inlet/outlet clearance.
Pools
A rectangular pool's water volume: average depth × length × width = cubic feet; × 7.48 = gallons. A 20 × 10 × 5 ft pool holds 7,480 gallons.
Conversion Table
| Cubic Feet | US Gallons | Imperial Gallons | Liters |
|---|---|---|---|
| 1 | 7.48 | 6.23 | 28.32 |
| 2 | 14.96 | 12.46 | 56.63 |
| 5 | 37.4 | 31.14 | 141.58 |
| 10 | 74.81 | 62.29 | 283.17 |
| 25 | 187.01 | 155.72 | 707.92 |
| 50 | 374.03 | 311.44 | 1,415.84 |
| 100 | 748.05 | 622.88 | 2,831.68 |
Water Storage and Tank Sizing
Water storage and rainwater harvesting tanks list capacity in gallons, but the tank itself is built and shipped by volume in cubic feet. To size a cylindrical tank, calculate cubic feet with the cylinder volume calculator (π × radius² × height), then multiply by 7.48 for US gallons. For rectangular cisterns, use the main cubic feet calculator with length, width and height, then apply the same 7.48 multiplier. Always subtract 5–10% of the calculated volume for the air gap suppliers recommend below the fill line.
Frequently Asked Questions
How many gallons are in a cubic foot?
1 cubic foot = 7.48052 US gallons or 6.22884 Imperial gallons.
How many liters in a cubic foot?
1 cubic foot = 28.3168 liters.
How do I calculate aquarium volume in gallons?
Multiply L × W × H in inches, divide by 231 (cubic inches per US gallon). Or calculate cubic feet and multiply by 7.48.
How big is a 10-gallon tank in cubic feet?
10 US gallons = 1.337 cubic feet.
Are US and Imperial gallons the same?
No. 1 US gallon = 3.785 L. 1 Imperial gallon = 4.546 L. Imperial gallons are about 20% larger.
How many gallons in a 55-gallon drum?
By name, 55 US gallons = 7.35 ft³ = 208.2 L. Actual usable capacity is typically 53–55 gallons.
How do I convert a pool's cubic feet to gallons?
Multiply pool cubic feet by 7.48 for US gallons. A 20 × 10 × 5 ft pool holds 1,000 ft³ × 7.48 = 7,480 gallons.
How many cubic feet in 100 gallons?
100 US gallons = 13.37 cubic feet.