Cubic Feet to Gallons (ft³ to gal)
One cubic foot holds 7.48052 US gallons. Both units are defined exactly — a foot is 0.3048 m and a US gallon is 231 cubic inches (NIST SP 811) — so the factor is 1,728 ÷ 231 = 7.480519…, and multiplying by 7.48 is accurate to better than 0.01%.
Formula
gallons = cubic feet × 7.48052
Example: 3 cubic feet = 22.4416 gallons.
Cubic Feet to Gallons chart
| cubic feet | gallons |
|---|---|
| 0.5 | 3.74026 |
| 1 | 7.48052 |
| 2 | 14.961 |
| 3 | 22.4416 |
| 5 | 37.4026 |
| 10 | 74.8052 |
| 20 | 149.61 |
| 27 | 201.974 |
| 50 | 374.026 |
| 100 | 748.052 |
| 250 | 1,870.13 |
| 500 | 3,740.26 |
| 1,000 | 7,480.52 |
| 5,000 | 37,402.6 |
| 10,000 | 74,805.2 |
Good to know
Pools, ponds and tanks are where this comes up most. Measure length × width × average depth in feet to get cubic feet, then multiply by 7.48: a 20 ft × 10 ft pool with an average depth of 5 ft holds 1,000 ft³, or 7,480.5 US gallons. Round shapes use π × radius² × depth for the cubic feet.
UK and older Canadian figures use the imperial gallon (4.54609 L), which is about 20% larger, so 1 ft³ is only 6.22884 imperial gallons. Water-heater, refrigerator and soil-bag volumes in the US are in US gallons and cubic feet.
Frequently asked questions
How many gallons are in a cubic foot?
7.48052 US gallons (exactly 1,728 ÷ 231), or 6.22884 imperial gallons.
How many gallons is 1,000 cubic feet?
1,000 ft³ is 7,480.52 US gallons.
How do I find the gallons in a pool?
Multiply length × width × average depth in feet for cubic feet, then multiply by 7.48. A 20 × 10 ft pool with a 5 ft average depth holds about 7,480 gallons.