In process engineering, accurately measuring fluid movement is critical for system design. The Gallon per minute (GPM) is a standard US customary unit used primarily in hydraulic systems, fire protection, and residential plumbing to quantify liquid flow. Conversely, the Cubic foot per minute (CFM) is a unit of volumetric flow rate often used in HVAC systems, pneumatic conveying, and gas processing.
Converting between these units is essential when transitioning from liquid-based hydraulic calculations to gas-based or bulk-volume system requirements. The conversion factor is derived from the volume of one US gallon, which is exactly 231 cubic inches. Since one cubic foot contains 1,728 cubic inches, the conversion factor is calculated as \(\frac{231}{1728} \approx 0.13368\).
GPM Applications: Pump sizing, irrigation flow, and municipal water distribution.
CFM Applications: Air compressor output, ventilation requirements, and industrial dust collection systems.
Gallon per minute (US) to Cubic foot per minute Conversion Reference Table
Gallon per minute (US) (GPM)
Cubic foot per minute (CFM)
0.1
0.0134
0.5
0.0668
1.0
0.1337
2.0
0.2674
5.0
0.6684
10.0
1.3368
20.0
2.6736
50.0
6.684
100.0
13.3681
500.0
66.8403
1000.0
133.6806
Conversion Example: 10 GPM to CFM
To convert a flow rate from GPM to CFM, multiply the GPM value by the conversion factor of 0.13368055561220618.
This factor is derived from the ratio of the volume of a US gallon (231 cubic inches) to the volume of a cubic foot (1,728 cubic inches). Dividing 231 by 1,728 yields approximately 0.13368.
No. This conversion factor is specific to US liquid gallons. Imperial gallons have a different volume (approximately 277.42 cubic inches), which would require a different conversion constant.
"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)