How To Calculate Air Compressor CFM to kW

June 10, 2023

People have been asking how to calculate air compressor CFM to kW, and we want to help tackle the question. But first and foremost, it’s essential to understand that CFM and kW are not directly convertible metrics.

CFM refers to Cubic Feet per Minute, which measures volume of air coming out of an air compressor each minute. kW, on the other hand, represents kilowatts or the amount of energy required to power an air compressor.

Comparing CFM to kW is like comparing apples and oranges. But we can take that analogy one step further: where apples and oranges are still related because they are both fruit, CFM and kW are related. After all, they both influence an air compressor’s capabilities.

How To Convert kW To CFM For Air Compressors

As a rule, one kW can generate 3-4 CFM for mobile air compressor applications. Check out the quick reference chart below to see how this impact outputs:

Power Output (kW) CFM Output
5 15 - 20
10 30 - 40
25 75 - 100
50 150 - 200
100 300 - 400
250 750 - 1,000

Engineers must utilize an engine that produces the right kW when designing an air compressor system. Too little kW and the desired CFM won’t be achieved. Too much, and the system costs more than it needs to. Understanding the relationship between kW and CFM helps air compressor engineers choose suitable engines for their systems.

Let’s take a quick look at two of VMAC’s rotary screw products as examples:

Product Engine Power Output CFM Output
G30 Gas Drive Honda GX390 8.7 kW @ 3,600 rpm 30 CFM
D60 Diesel Drive Kubota D902 15.2 kW @ 3,600 rpm 60 CFM

As you can see, these VMAC systems produce 3-4 CFM per kW.

Outputs are similar when looking at one of VMAC’s direct competitors. Their gas driven rotary screw air compressor uses a Kohler 26.5 HP engine with 19.75 kW of power to produce 60-80 CFM. This math works out to the same 3-4 CFM per kW output as the VMAC systems.

Keep in mind that the Honda, Kubota, and Kohler engines in the examples above are likely capable of producing higher CFM outputs under the right circumstances, but real-world designs put these systems in the 3-4 CFM per kW range. Therefore, an accurate estimate of kW to CFM (and vice versa) for mobile, rotary screw air compressor applications is 3-4 CFM per 1 kW.