Fan Brake Horsepower Calculator
Shaft power required to move air against a fan's static pressure.
Enter your values
ⓘ Live results
Results
- Brake horsepower
- 7.26 hp
- Air power
- 4.72 hp
- Motor size (1.15 SF)
- 8.35 hp
- Electrical input at 90% motor eff
- 6.02 kW
Quick answer
Brake horsepower equals CFM times total pressure in inches of water, divided by 6356 times the fan's total efficiency.
BHP = CFM x TP(in wc) / (6356 x eff)
How to use the Fan Brake Horsepower Calculator
- 1Enter the design CFM and total pressure from the fan curve.
- 2Enter the fan's total efficiency at that operating point, from the manufacturer's curve.
- 3Size the motor with a service factor above the calculated brake horsepower.
Worked example
Using the values the calculator loads with:
Inputs
- Airflow10000 CFM
- Total pressure3.0 in wc
- Fan total efficiency65 %
Results
- Brake horsepower7.26 hp
- Air power4.72 hp
- Motor size (1.15 SF)8.35 hp
- Electrical input at 90% motor eff6.02 kW
Frequently asked questions
Total pressure or static pressure?
Use total pressure (static plus velocity) for true brake horsepower; static-only understates power for high-velocity fans.
Where does 6356 come from?
It converts CFM x inches of water into horsepower (33,000 ft-lb/min per hp with unit conversions).
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.