Convert Pounds per Gallon to Pounds per Cubic Inch

Formula

lb/in³ = lb/gal ÷ 231

Derivation from SI units:

• 1 lb/gal = 0.45359237 kg ÷ 0.003785411784 m³ = 119.8264273 kg/m³
• 1 lb/in³ = 0.45359237 kg ÷ 1.6387064 × 10⁻⁵ m³ = 27 679.9047 kg/m³
• 1 lb/gal = 119.8264273169 kg/m³ ÷ 27679.9047102 kg/m³ per lb/in³ = 0.004329004329004 lb/in³

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

Worked examples

1. A reading of 7.1 lb/gal converts to 0.03073593074 lb/in³.
   7.1 lb/gal × 0.004329004329 = 0.03073593074 lb/in³
2. A value of 10 lb/gal is 0.04329004329 lb/in³.
   10 lb/gal × 0.004329004329 = 0.04329004329 lb/in³

Where it's used

Pounds per Gallon are used for drilling-mud weight in the oil and gas industry (ppg), while pounds per cubic inch appear in metal densities (steel ≈ 0.284 lb/in³, aluminium ≈ 0.098 lb/in³). Both measure density (mass per unit volume) and mass concentration, so the conversion is a fixed factor.

Pound per Gallon to other density 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, "pound per gallon (U.S.)".
• 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, "pound per cubic inch (lb/in³)".

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