Oh, I meant it would be a conservative value because it is being
measured above rather than at the specified pressure.


Richard Ferguson wrote:
I don't know about a conservative value, but you would have a ballpark
value. You can use the reverse process to figure CFM for tools, turn
off the compressor and measure the time it takes the tool to drop the
tank presssure from 105psi to 90 psi. As others have noted, the
measured CFM for a compressor will probably be less than the published
CFM, while the measured CFM for a tool will probably be more than the
published CFM. :-( In other words, get a bigger compressor than the
CFM numbers suggest would be adequate.

You would need to convert gallons to cubic feet, but the sample
calculation showed the conversion factor.

Richard

Dave wrote:

Thanks, that is very straightforward. So if I measure the time from
60psi to 75psi and plug that in I should get a conservative value of
true CFM for 60psi ?