Free Tool by AirGen Compressors

Compressor CFM Calculator

Measure your compressor's actual Free Air Delivery (FAD) using a simple tank fill test. Enter your readings below to get instant, accurate results.

Test Inputs Tank fill method

Litres
bar g
bar g
Minutes
min
Seconds
sec

bar abs
ⓘ Note on atmospheric pressure:
The standard value is 1.01325 bar abs (sea level, 15 °C). However, this value varies with your location and altitude:

• At higher altitudes (e.g. hill stations, highlands), atmospheric pressure is lower — this reduces compressor output.
• On a hot day or in humid conditions, actual pressure may differ slightly.
• For most industrial sites in Pune / Maharashtra, 1.013 bar is accurate. If your site is at significant elevation, use a local barometer reading for best accuracy.

How It Works Tank fill test guide

1
Empty the receiver tank
Drain the tank to zero (or known start) pressure. Close all air outlets.
2
Start the compressor & timer
Start your stopwatch exactly when the compressor starts filling the tank.
3
Stop at target pressure
Stop the timer when the gauge reaches your end pressure. Record both values.
4
Enter your readings
Fill in the form on the left — results update instantly.

Formula Used
FAD = V × (P2−P1) / Patm
Flow = FAD / Fill Time
Where V = tank volume (L), P1/P2 = gauge pressures (bar), Patm = atmospheric pressure (bar abs)

Live Results Updates as you type

Free Air Delivery (FAD) — Flow Rate
CFM
124.0
ft³/min
m³/min
3.51
cubic metres/min
L/s
58.5
litres per second
Test Summary
Free Air Volume
7895
litres
Fill Time
135
seconds
Pressure Rise
8.0
bar