Convert Gallons per Minute to Cubic Feet per Minute

Formula

CFM = GPM × 0.1336805555556

or CFM = GPM ÷ 7.480519480519

Derivation from SI units:

• 1 GPM = 231 in³ ÷ 60 s = 0.003785411784 m³ ÷ 60 s = 6.30901964 × 10⁻⁵ m³/s
• 1 CFM = (0.3048 m)³ ÷ 60 s = 4.719474432 × 10⁻⁴ m³/s
• 1 GPM = 0.0000630901964 m³/s ÷ 0.0004719474432 m³/s per CFM = 0.1336805555556 CFM

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

Worked examples

1. A reading of 3 GPM converts to 0.4010416667 CFM.
   3 GPM × 0.1336805556 = 0.4010416667 CFM
2. A value of 25 GPM is 3.342013889 CFM.
   25 GPM × 0.1336805556 = 3.342013889 CFM

Where it's used

Gallons per Minute are used for pump, well and irrigation ratings, while cubic feet per minute appear in US HVAC airflow (about 400 CFM per ton of cooling). Both measure volumetric flow rate (volume per unit time), so the conversion is a fixed factor.

Gallon per Minute to other flow rate 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.] per minute (gpm)".
• 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 per minute (ft³/min)".

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