SCFM to ACFM (Fan) Calculator
Convert standard CFM to actual CFM at fan operating conditions.
Enter your values
ⓘ Live results
Results
- Actual CFM (ACFM)
- 7,204 ACFM
- Temperature ratio
- 1.34
- Pressure ratio
- 1.075
Quick answer
Actual CFM equals standard CFM multiplied by the ratio of standard absolute temperature and pressure to actual absolute temperature and pressure.
ACFM = SCFM x (T_actual/T_std) x (P_std/P_actual)
How to use the SCFM to ACFM (Fan) Calculator
- 1Enter the standard CFM (measured or rated at 70F, sea level).
- 2Enter the actual operating temperature and site altitude.
- 3Read the actual CFM, which the fan physically moves at those real conditions — always larger than SCFM at high temperature.
Worked example
Using the values the calculator loads with:
Inputs
- Standard CFM5000 SCFM
- Actual temperature250 F
- Altitude2000 ft
Results
- Actual CFM (ACFM)7,204 ACFM
- Temperature ratio1.34
- Pressure ratio1.075
Frequently asked questions
Why does ACFM increase with temperature?
Hot gas expands, so the same mass flow occupies a larger actual volume, even though standard (mass-equivalent) flow is unchanged.
Which do I size the fan wheel on?
Always size the fan wheel and duct velocity on ACFM, since that is the real physical volume moving through the system.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.