Convert US Gallons to Cubic Inches

Formula

in³ = gal (US) × 231

Derivation from SI units:

• 1 US gal = 231 in³ = 231 × (0.0254 m)³ = 0.003785411784 m³
• 1 in³ = (0.0254 m)³ = 1.6387064 × 10⁻⁵ m³ = 16.387064 cm³
• 1 gal (US) = 0.003785411784 m³ ÷ 0.000016387064 m³ per in³ = 231 in³

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

Worked examples

1. A reading of 10 gal (US) converts to 2310 in³.
   10 gal (US) × 231 = 2310 in³
2. A value of 100 gal (US) is 23100 in³.
   100 gal (US) × 231 = 23100 in³

Where it's used

US Gallons are used for fuel, water and chemical volumes in the US, while cubic inches appear in US engine displacement (e.g. 350 cubic inches ≈ 5.7 L). Both measure volume (capacity), so the conversion is a fixed factor.

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 inch (in³)".

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