Cubic Feet per Minute (CFM) is the most common imperial unit for measuring volumetric flow. The unit describes water that moves through a pipe, effluent that leaves a plant or air that flows through a ventilation duct. A particularly high rate of flow might use the alternate unit of gallons per second. You can easily convert between the two units, which use the same linear scale and the same system of measurement.

Multiply the flow rate by 4 to convert it to quarts per second. If, for instance, you are converting a flow of 5 g/s -- 5 × 4 = 20 quarts per second (qt/s).

Multiply this result by 60 to convert it to quarts per minute -- 20 × 60 = 1,200 qt/min.

Divide this result by 29.92 to convert it to cubic feet per minute -- 1,200 ÷ 29.92 = 40.1 CFM.

#### Tip

To convert with a single step, multiply by 8.021.