How to Calculate CFM?

CFM stands for “cubic feet per minute” and is a measure of air flow, often used to describe the capabilities of heating, ventilation and air conditioning systems.

It describes the rate at which a certain volume of air moves in a certain period of time. In the case of a blower or fan, it indicates how much air it can move per minute. So for example, a 1,000 cfm fan can remove all of the air from a box that is 10ft x 10ft x 10ft in one minute.

The most common use for this formula is when installing a bathroom fan.

1. If a bathroom is 8′ x 8′ with 8′ ceiling, that equals 512 cubic feet.

2. If there’s a need to turn the air over 5 times in an hour, a total of 2,560 cubic feet of air will need to be moved.

3. Take 2,560 cubic feet , divide it by one hour (60 min), equals 42.6 cfm

The conclusion is that a fan of at least 42.6cfm will be needed to do the job.