Enter the fan flow rate (CFM), the total pressure (in. wg), and the fan power input (hp) into the calculator to determine the Fan Efficiency.

## Fan Efficiency Formula

The following formula is used to calculate the Fan Efficiency.

Efan = FR * Pt/ (6343 * Pi)*100

• Where Efan is the Fan Efficiency (%)
• FR is the fan flow rate (CFM)
• Pt is the total pressure (in. wg)
• Pi is the fan power input (hp)

## How to Calculate Fan Efficiency?

The following example problems outline how to calculate the Fan Efficiency.

Example Problem #1

1. First, determine the fan flow rate (CFM). In this example, the fan flow rate (CFM) is given as 400 .
2. Next, determine the total pressure (in. wg). For this problem, the total pressure (in. wg) is given as  30 .
3. Next, determine the fan power input (hp). In this case, the fan power input (hp) is found to be 20.
4. Finally, calculate the Fan Efficiency using the formula above:

Efan = FR * Pt/ (6343 * Pi)

Inserting the values from above and solving yields:

Efan = 400 * 30/ (6343 * 20) *100 = 9.45 (%)

Example Problem #2

Using the same method as above, determine the variables required by the equation. For this example problem, these are provided as:

fan flow rate (CFM) = 500

total pressure (in. wg) = 30

fan power input (hp) = 10

Enter these given values yields:

Efan = 500 * 30/ (6343 * 10)*100 = 23.648 (%)