Convert US Gallons to Cubic Feet

Formula

ft³ = gal (US) × 0.1336805555556

or ft³ = gal (US) ÷ 7.480519480519

Derivation from SI units:

• 1 US gal = 231 in³ = 231 × (0.0254 m)³ = 0.003785411784 m³
• 1 ft³ = (0.3048 m)³ = 0.028316846592 m³
• 1 gal (US) = 0.003785411784 m³ ÷ 0.028316846592 m³ per ft³ = 0.1336805555556 ft³

Both units are defined exactly, so the factor is exact. US Gallon definition: US gallon; Cubic Foot definition: cubic foot.

Worked examples

1. 7.48 gal (US) is almost exactly 0.9999305556 ft³.
   7.48 gal (US) × 0.1336805556 = 0.9999305556 ft³
2. A 100 gal (US) tank holds 13.36805556 ft³.
   100 gal (US) × 0.1336805556 = 13.36805556 ft³

Where it's used

Tank, pond and pool volumes in gallons are converted to cubic feet for space, weight and fill-time calculations.

US Gallon to other volume units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "gallon [U.S.] (gal)".
• NIST Handbook 44, Appendix C: General Tables of Units of Measurement, National Institute of Standards and Technology , Appendix C.
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "cubic foot (ft³)".

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.