Convert Cubic Feet to US Gallons

Formula

gal (US) = ft³ × 7.480519480519

Derivation from SI units:

• 1 ft³ = (0.3048 m)³ = 0.028316846592 m³
• 1 US gal = 231 in³ = 231 × (0.0254 m)³ = 0.003785411784 m³
• 1 ft³ = 0.028316846592 m³ ÷ 0.003785411784 m³ per gal (US) = 7.480519480519 gal (US)

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

Worked examples

1. 1 ft³ holds 7.480519481 gal (US).
   1 ft³ × 7.480519481 = 7.480519481 gal (US)
2. A 50 ft³ hot tub holds about 374.025974 gal (US).
   50 ft³ × 7.480519481 = 374.025974 gal (US)

Where it's used

Volumes measured as length × width × depth in feet are converted to gallons to size pumps, chemicals and water bills.

Cubic Foot 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, "cubic foot (ft³)".
• 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.

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