Measuring air compressor CFM output?

[SecondMonkey]

Today the rating on most air compressors is more than what you get in real life. I have a few such examples, and some homemade things, that I'd like to test the CFM output at certain pressures. For that matter, I'd like to be able to measure the actual useage of some of my tools, too. Is there some kind of tool or device that I can buy or make to measure actual CFM output?

 

[XS650]

A trash bag of known capacity and a stopwatch.

It won't be perfectly accurate but it will be consistent if you take some care.

 

[Shannow]

If you've got access to a pool, you could make a "gasometer" out of an inverted rubbish bin.

 

[94MaxGXE]

You may find this info interesting.


Evaiuating True HP and CFM.