Gallons ↔ Cubic Feet Converter
Convert between US gallons (gal) and cubic feet (ft³) instantly — both ways. Type in either box and the other updates live, with bonus conversions to liters, imperial gallons and cubic meters.
Type a value in either box — the other converts automatically. Uses US liquid gallons.
Controls how the converted values are rounded.
| Unit | Value |
|---|---|
| Convert to see all units | |
How to use the gallons to cubic feet converter
Type into either box and the other updates as you go — US gallons to cubic feet, or cubic feet back to gallons, plus liters, imperial gallons, cubic meters, and a report you can download.
Type into either box
Enter US gallons or cubic feet — whichever your tank spec or utility bill uses. The other converts live.
Set the rounding
Auto handles most figures. Lock it to fixed decimals when you need to match a datasheet or a meter reading.
Check the equivalents
See the volume in 5-gallon buckets, bathtubs, and water heaters — a quick sanity check on the number.
Read all units & save a PDF
Eight conversions, the side-by-side scale diagram, and a report you can keep or send on.
How the conversion is calculated
A cubic foot is 1,728 cubic inches. A US gallon is defined as 231 cubic inches. Divide one by the other and you get 7.48052 — the whole conversion in a single ratio, and the reason the number looks so odd.
Worked example — a 16 × 32 ft pool, 5 ft average depth
Volume: 16 × 32 × 5 = 2,560 ft³
US gallons: 2,560 × 7.48052 = 19,150 gal
Liters: 2,560 × 28.3168 = 72,491 L
Weight of water: 19,150 × 8.34 ≈ 159,700 lb
≈ 19,150 gallons — the figure every chemical dose, heater, and pump spec will ask for.
Gallons and cubic feet conversion charts
The lookups that come up most — the conversion both ways, one cubic foot in every unit, the water-bill units that confuse everyone, and the tank and pool volumes people search by name.
| US gallons | Cubic feet | Liters | Imperial gallons |
|---|---|---|---|
| 1 gal | 0.1337 ft³ | 3.79 L | 0.83 gal |
| 5 gal | 0.6684 ft³ | 18.93 L | 4.16 gal |
| 10 gal | 1.3368 ft³ | 37.85 L | 8.33 gal |
| 25 gal | 3.3420 ft³ | 94.64 L | 20.82 gal |
| 50 gal | 6.6840 ft³ | 189.27 L | 41.63 gal |
| 100 gal | 13.3681 ft³ | 378.54 L | 83.27 gal |
| 500 gal | 66.8403 ft³ | 1,892.71 L | 416.34 gal |
| 748.05 gal | 100.0000 ft³ | 2,831.68 L | 622.88 gal |
| 1,000 gal | 133.6806 ft³ | 3,785.41 L | 832.67 gal |
The 748.05 row is worth memorising — that’s exactly 100 cubic feet, or one CCF, which is how most US water utilities meter and bill.
| Cubic feet | US gallons | Liters | Water weight |
|---|---|---|---|
| 1 ft³ | 7.48 gal | 28.32 L | 62.4 lb |
| 5 ft³ | 37.40 gal | 141.58 L | 312 lb |
| 10 ft³ | 74.81 gal | 283.17 L | 624 lb |
| 25 ft³ | 187.01 gal | 707.92 L | 1,560 lb |
| 50 ft³ | 374.03 gal | 1,415.84 L | 3,120 lb |
| 100 ft³ | 748.05 gal | 2,831.68 L | 6,240 lb |
| 500 ft³ | 3,740.26 gal | 14,158.42 L | 31,200 lb |
| 1,000 ft³ | 7,480.52 gal | 28,316.85 L | 62,400 lb |
Water weight is approximate, at roughly 8.34 lb per US gallon at room temperature. It varies slightly with temperature and rises with anything dissolved in the water.
| Unit | 1 cubic foot equals | Where you’ll see it |
|---|---|---|
| US gallons | 7.480519 gal | Tanks, pools, plumbing specs |
| Imperial gallons | 6.228835 gal | UK and Commonwealth figures |
| Liters | 28.316847 L | Imported equipment ratings |
| Cubic inches | 1,728 in³ | Component and fitting specs |
| Cubic yards | 0.037037 yd³ | Bulk material ordering |
| Cubic meters | 0.0283168 m³ | Metric plans and datasheets |
| US fluid ounces | 957.51 fl oz | Small-volume dosing |
The calculator lists all of these at once in the all-units table, so you can copy whichever basis your spec or bill is written in.
| Unit on the bill | What it means | In US gallons |
|---|---|---|
| 1 CCF | One hundred cubic feet | 748.05 gal |
| 1 HCF | Hundred cubic feet — same as CCF | 748.05 gal |
| 1 unit | Usually 100 cubic feet | 748.05 gal |
| 1 kgal | One thousand gallons | 1,000 gal |
| 1 cubic foot | The base meter increment | 7.48 gal |
| 1 acre-foot | 43,560 cubic feet | 325,851 gal |
CCF and HCF are the same unit under two names, and “unit” almost always means the same thing again. If your bill shows 8 units, that’s roughly 5,984 gallons. Check the meter face, which usually states its own increment.
| Item | US gallons | Cubic feet | Water weight |
|---|---|---|---|
| Bucket | 5 gal | 0.67 ft³ | 42 lb |
| Bathtub | 40 gal | 5.35 ft³ | 334 lb |
| Water heater | 50 gal | 6.68 ft³ | 417 lb |
| Rain barrel | 55 gal | 7.35 ft³ | 459 lb |
| Large water heater | 80 gal | 10.69 ft³ | 667 lb |
| Storage tank | 500 gal | 66.84 ft³ | 4,170 lb |
| Cistern | 1,000 gal | 133.68 ft³ | 8,340 lb |
Rated capacity is nominal. Actual fill volume is lower once you account for the fill line, fittings, and any air gap, and tank exterior dimensions are larger than the water volume suggests.
| Pool | Average depth | Cubic feet | US gallons |
|---|---|---|---|
| 12 × 24 ft rectangular | 4.5 ft | 1,296 ft³ | ≈ 9,695 gal |
| 16 × 32 ft rectangular | 5 ft | 2,560 ft³ | ≈ 19,150 gal |
| 18 × 36 ft rectangular | 5.5 ft | 3,564 ft³ | ≈ 26,661 gal |
| 20 × 40 ft rectangular | 6 ft | 4,800 ft³ | ≈ 35,907 gal |
| 15 ft round | 4 ft | 707 ft³ | ≈ 5,288 gal |
| 24 ft round | 4 ft | 1,810 ft³ | ≈ 13,536 gal |
| 27 ft round | 4.5 ft | 2,577 ft³ | ≈ 19,273 gal |
Average depth, not deep-end depth. On a sloping floor, add shallow and deep depths and halve them — using the deep end alone can overstate volume by thousands of gallons and lead to over-dosing chemicals.
The cubic foot is a tidy 12 × 12 × 12 inch cube. The US gallon was fixed at 231 cubic inches centuries earlier, for entirely unrelated reasons. Divide one by the other and 7.48052 falls out.
- Neither number is rounded — 1,728 and 231 are both exact definitions, so 7.480519 is an exact ratio rather than an approximation.
- Imperial gallons break the math — at 277.42 in³, a cubic foot holds only 6.23 of them. Always check which gallon a figure means.
- Volume implies weight — water runs about 8.34 lb per gallon, so a tank’s capacity is also a structural question for the floor under it.
Everything the converter works out
One figure in either box gives you the full picture — the conversion both ways, the same volume in every unit, a scale you can actually picture, and a report you can keep.
The figures behind every cubic foot
Built for anyone sizing water by volume
Tanks are sold in gallons, meters read in cubic feet, and equipment is often rated in liters — so at least one conversion sits between you and the answer.
Working out true pool volume in gallons so chemical doses, filter turnover, and heater sizing all rest on the same number rather than a guess.
- Use average depth, not deep end
- Recalculate after any resurfacing
- Keep the figure on file for dosing
Translating a water bill quoted in CCF, HCF, or “units” into gallons, so usage can be compared against fixtures, leaks, and last year’s statement.
- 1 CCF = 748 gallons
- Check the meter’s own increment
- Compare month to month, not to averages
Sizing tanks, cisterns, and pumps where capacity is quoted in gallons but the space, spec sheet, or imported equipment is described in cubic feet or liters.
- Separate water volume from footprint
- Check loading before siting a tank
- Save the PDF against the job file
7 tips for getting water volume right
The slips that quietly throw a volume figure off — and the checks that catch them before anything is ordered or dosed.
Gallons to cubic feet FAQ
The conversion, billing, and capacity questions people ask most when a volume is quoted in the unit they don’t use.
One cubic foot holds about 7.48052 US gallons. Going the other way, one US gallon is 0.133681 ft³.
The figure looks arbitrary but it’s exact: a cubic foot is 1,728 cubic inches and a US gallon is defined as 231 cubic inches, and 1,728 ÷ 231 = 7.48052.
Multiply the gallons by 0.133681, or divide by 7.48052 — the two are the same operation. A 50 gallon water heater comes to 50 × 0.133681 = 6.68 ft³.
If you’re starting from dimensions in feet, multiply length by width by height for cubic feet first, then multiply by 7.48052 to get gallons.
CCF and HCF both mean one hundred cubic feet, and they’re the same unit. One CCF is 748 US gallons, or 2.83 cubic meters.
Many US water utilities bill in CCF rather than gallons, so a bill showing 8 CCF represents roughly 5,984 gallons of use. Some utilities bill per thousand gallons instead, which is 133.68 cubic feet.
For a rectangular pool, multiply length × width × average depth in feet, then by 7.48. A 16 by 32 foot pool averaging 5 feet deep is 2,560 cubic feet, or about 19,150 gallons.
For a round pool, multiply 3.1416 × radius² × depth × 7.48. Use average depth rather than deep-end depth on any pool with a sloping floor, or the figure will come out far too high.
No. A US gallon is 231 cubic inches or 3.785 liters, while an imperial gallon is about 277.42 in³ or 4.546 liters — roughly 20 percent larger.
That means one cubic foot holds 7.48 US gallons but only 6.23 imperial gallons. UK, Canadian, and older Commonwealth figures often use the imperial gallon, so check which one a spec means before converting.
About 62.4 pounds at room temperature, since water weighs roughly 8.34 lb per US gallon and a cubic foot holds 7.48 gallons.
This matters more often than people expect. A 50 gallon water heater holds around 417 lb of water on its own, and a modest 100 gallon tank puts over 800 pounds on whatever surface is beneath it.
A 50 gallon tank holds about 6.68 cubic feet of water. An 80 gallon tank is roughly 10.69 ft³, and a 40 gallon tank about 5.35 ft³.
Those figures describe the water volume, not the appliance footprint. The physical unit is larger once insulation, jacket, and fittings are included, so use manufacturer dimensions when checking whether it fits a closet.
Because the two units come from different traditions. The cubic foot is a straightforward 12 × 12 × 12 inch cube, which is 1,728 cubic inches. The US gallon descends from the old English wine gallon and was fixed at 231 cubic inches.
Divide 1,728 by 231 and you get 7.48052. The awkward figure is simply the ratio between a decimal-friendly cube and a historical liquid measure that was never designed to match it.
Planning Estimate Only — Not a Metered or Engineered Figure: This converter changes the volume you enter between US gallons, cubic feet, and other units using exact conversion factors, and uses US liquid gallons throughout. Tank, appliance, and pool capacities shown on this page are nominal industry figures that vary by manufacturer and installation; actual fill volume is lower once fill lines, fittings, air gaps, and sloping floors are accounted for. Water weight figures are approximate at room temperature and change with temperature and dissolved content — consult a qualified professional before siting a large tank or relying on floor loading. Billing units differ between utilities, so confirm your meter’s increment and your provider’s stated unit before comparing usage. For planning purposes only.