In process engineering, fluid dynamics often require the conversion between gas-phase volumetric units and liquid-phase volumetric units. The Cubic Foot per Minute (CFM) is a standard imperial unit used to measure the flow rate of air or gas, while the US Gallon per Minute (GPM) is the standard for liquid flow measurement.
CFM: Primarily used in HVAC systems, pneumatic conveying, and compressor output ratings.
GPM: Essential for pump sizing, hydraulic systems, and water treatment facility throughput.
The conversion factor is derived from the volume of one cubic foot, which is exactly 7.480519477349415 US gallons. Therefore, to convert a flow rate from CFM to GPM, we use the following relationship: \( Q_{\text{GPM}} = Q_{\text{CFM}} \times 7.480519477349415 \).
Cubic foot per minute to Gallon per minute (US) Conversion Reference Table
Cubic foot per minute (CFM)
Gallon per minute (US) (GPM)
0.1
0.7481
0.5
3.7403
1.0
7.4805
2.0
14.961
5.0
37.4026
10.0
74.8052
20.0
149.6104
50.0
374.026
100.0
748.0519
500.0
3740.2597
1000.0
7480.5195
Conversion Example: 10 CFM to GPM
To convert a flow rate of 10 CFM into GPM, multiply the value by the conversion factor:
Rounding to two decimal places, 10 CFM is equivalent to 74.81 GPM.
The factor 7.48052 is derived from the definition of a US liquid gallon, which is defined as 231 cubic inches. Since one cubic foot contains 1,728 cubic inches (12 x 12 x 12), dividing 1,728 by 231 yields approximately 7.480519.
Yes, this conversion is mathematically valid for volume. However, note that air is compressible, so 1 CFM of air at high pressure occupies a different mass than 1 CFM at atmospheric pressure. Always ensure your pressure and temperature conditions are normalized when performing fluid calculations.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)