A variation on that theme is to measure the time required to increase
the pressure of the tank by 15 psi (14.7psi is atmospheric pressure at
sea level.)

Let me try a sample calculation.

25 gallon tank x 0.1337 cuft/gal = 3.34 cubic feet

If it takes 30 seconds to increase the tank pressure 15 psi, it would
take one minute to increase the tank pressure 30 psi (disregarding
efficiencies). 30 seconds is half a minute.

3.34 cubic feet / 0.5 minute = 6.68 CFM

Richard



Nick Müller wrote:
Dave wrote:


Anyone here know of a table or spreadsheet anywhere online that will
allow you to estimate the actual approximate CFM rating of a
compressor?


Volume (of tank) * pressure (in tank; value in bar) = aspirated volume.
If the tank is pressure-less, start your stopwatch, stop it when it is
full.
Divide aspirated volume by that time (in minutes).
That's only a guesstimate, because efficency will decrease with rising
pressure and the formula also doesn't consider rise of temperature. But
you have a good ballpark.


Nick


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