Whether the number came from a water bill, a pool plan or a tank spec sheet, everything rests on one conversion: 1 cubic foot is 7.4805 US gallons. The sections below show how to use it, with the common values already worked out.
📋 Table of Contents
One cubic foot of water in gallons, liters and pounds
The 7.48 figure comes straight from the definition of the gallon. NIST Handbook 44 (Appendix C) defines the US liquid gallon as 231 cubic inches, and a cubic foot is 12 × 12 × 12 = 1,728 cubic inches, so a cubic foot holds 1,728 ÷ 231 = 7.4805 gallons. That is exact by definition; 7.48 is simply the rounded form.
| One cubic foot of water equals | Amount |
|---|---|
| US gallons | 7.4805 gal |
| US quarts | ≈ 29.92 qt |
| Liters | ≈ 28.32 L |
| Cubic inches | 1,728 in³ |
| Weight (cool water) | ≈ 62.4 lb (28.3 kg) |
For everyday jobs, use 7.48. Rounding up to 7.5 is quicker but runs about 0.26 percent high, which adds up on big volumes: a 10,000-gallon pool calculated with 7.5 comes out about 26 gallons over. The weight is worked out from the USGS water density table and shifts a little with temperature; our guide to how much a gallon of water weighs shows how it moves from cold to boiling.
Cubic feet to gallons: formula and chart
📐 Formula
Gallons = Cubic feet × 7.4805
Cubic feet = Gallons ÷ 7.4805
Example: 300 cubic feet × 7.4805 = 2,244 gallons. In reverse, 1,000 gallons ÷ 7.4805 = 133.68 cubic feet.
| Cubic feet | US gallons | Weight of water | Note |
|---|---|---|---|
| 0.5 ft³ | 3.74 gal | ≈ 31.2 lb | — |
| 1 ft³ | 7.48 gal | ≈ 62.4 lb | 1 cubic foot |
| 2 ft³ | 14.96 gal | ≈ 124.7 lb | — |
| 5 ft³ | 37.40 gal | ≈ 311.8 lb | — |
| 10 ft³ | 74.81 gal | ≈ 623.7 lb | — |
| 25 ft³ | 187.0 gal | ≈ 1,559 lb | — |
| 50 ft³ | 374.0 gal | ≈ 3,118 lb | — |
| 100 ft³ | 748.1 gal | ≈ 6,237 lb | 1 CCF (100 ft³) |
| 500 ft³ | 3,740 gal | ≈ 31,185 lb | — |
| 1,000 ft³ | 7,481 gal | ≈ 62,370 lb | — |
Gallons to cubic feet
Going the other way, divide by 7.4805, which is the same as multiplying by 0.13368. This is the version you need when a tank, drum or pond is rated in gallons and you are checking whether it fits a space measured in feet.
| US gallons | Cubic feet | Example |
|---|---|---|
| 1 gal | 0.1337 ft³ | — |
| 5 gal | 0.6684 ft³ | — |
| 10 gal | 1.34 ft³ | — |
| 50 gal | 6.68 ft³ | — |
| 55 gal | 7.35 ft³ | 55-gallon drum |
| 100 gal | 13.37 ft³ | — |
| 500 gal | 66.84 ft³ | — |
| 1,000 gal | 133.68 ft³ | 1,000-gallon tank |
How to find the gallons in a pool, tank or aquarium
Most real-life cases start with dimensions, not a ready-made volume. Measure the length, width and water depth in feet, multiply them to get cubic feet, then multiply by 7.4805. If your measurements are in inches, skip the middle step: length × width × height in inches, divided by 231, gives gallons directly.
| Container | Working | Gallons |
|---|---|---|
| Aquarium, 48 × 18 × 21 in | 18,144 in³ ÷ 231 | ≈ 78.5 gal |
| Rectangular pool, 12 × 24 ft, 4 ft deep | 1,152 ft³ × 7.4805 | ≈ 8,618 gal |
| Round pool, 15 ft across, 3.5 ft deep | π × 7.5² × 3.5 = 618.5 ft³ | ≈ 4,627 gal |
| Rain barrel, 2 ft across, 3 ft tall | π × 1² × 3 = 9.42 ft³ | ≈ 70.5 gal |
Three details change the answer in practice. Use the depth of the water, not the height of the wall. For a pool that slopes, average the shallow and deep ends. And tanks are often sold by a rounded size: the aquarium above is sold as a 75-gallon tank but holds about 78.5 gallons to the brim, and you would never fill it that high.
Collecting rain? One inch of rain falling on 1,000 square feet of roof or paving is 83.3 cubic feet, which is about 623 gallons.
Cubic feet, CCF, cubic yards and other units
Water bills and supply plans use bigger units than a single cubic foot. Many utilities bill by the CCF, a hundred cubic feet, sometimes written HCF, which is about 748 gallons. If your meter reads in cubic feet, multiply the difference between two readings by 7.48 to see your usage in gallons.
| Unit | Cubic feet | US gallons |
|---|---|---|
| 1 cubic foot | 1 | 7.48 |
| 1 CCF (HCF) | 100 | 748.05 |
| 1 cubic yard | 27 | 201.97 |
| 1 cubic meter | 35.31 | 264.17 |
| 1 acre-foot | 43,560 | 325,851 |
For the smaller liquid units that sit under the gallon, our liquid measurement conversion chart lays out cups, pints and quarts in one place.
US, imperial and dry gallons
The 7.48 figure is for the US liquid gallon. If your source is British or uses UK units, a cubic foot holds fewer gallons, because the imperial gallon is larger. The US dry gallon, used for dry produce rather than liquids, is different again. Our US pint vs UK pint comparison shows the same US and UK split at the pint level.
| Gallon | Size | Gallons per cubic foot |
|---|---|---|
| US liquid gallon | 3.785 L | 7.4805 |
| UK imperial gallon | 4.546 L | 6.2288 |
| US dry gallon | 4.405 L | 6.4285 |