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Cubic Feet to Gallons Calculator

Convert a volume in cubic feet into US gallons — for tank capacity, pond volume and water storage.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Volume

74.81 US gallons

High confidence

1 US gallon = 231 in³ exactly, so 1 ft³ = 1728 / 231 ≈ 7.4805 gallons. Exact by definition — the only uncertainty is in your measurement of the vessel, not in the conversion.

Volume entered
10 ft³
Imperial gallons (UK)
62.29 imp gal
Litres
74.81 gal

Tank and vessel capacity is specified in gallons and measured in feet, which means this conversion sits between the tape measure and the order. It is the step where a pond liner, a rainwater butt or a plant room tank stops being a shape and becomes a number you can buy against.

Add the equipment this sizes

This result is a specification — 74.805 US gallons — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • NIST Handbook 44, Appendix C — 1 US liquid gallon = 231 cubic inches (exact)
  • 1 imperial gallon = 4.54609 L (exact), Weights and Measures Act 1985 (UK)

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Is this a US gallon or an imperial gallon?
The headline figure is US gallons, which is what tank and pump capacities are quoted in across North America. The imperial equivalent is shown in the breakdown — it is about 20% larger, so mixing the two undersizes a UK tank by a fifth.
How do I get cubic feet from a round tank?
Multiply π by the radius squared by the height, all in feet. A 6 ft diameter tank has a 3 ft radius, so π × 9 × height. Use the internal diameter, not the outside — on a thick-walled tank the difference is several percent of the volume.
Does this work for gas?
As a geometric volume, yes. As a quantity of gas, no — gas volume depends on pressure and temperature, so a cubic foot of propane at tank pressure is very much more than a cubic foot at atmospheric. Gas is bought by mass or by energy content for that reason.
Why does my tank hold less than this says?
Almost always freeboard. Tanks are rarely filled to the brim, and a stated capacity is usually the working volume rather than the geometric one. Baffles, internal fittings and a domed base all take their share too.