Fan Calculator: Power, Airflow, Efficiency and Fan Laws

Your details

Choose what to solve for. The affinity law mode scales an existing operating point to a new speed.
Volume of air the fan moves per minute (or per second for m³/s and L/s).
CFM
Total static pressure the fan must overcome (duct losses + filters + fittings).
in H₂O
Overall fan efficiency (air power out / shaft power in). Axial fans: 40-60%, centrifugal fans: 60-85%.
%
Shaft powerGood efficiency
90.4W

Power the motor must deliver to the fan shaft.

Air power58.8W
Brake horsepower0.121BHP
Air power (W)58.8
Shaft power (W)90.4

Shaft power required: 90.4 W (0.121 BHP) at 65.0% efficiency.

  • Air power delivered to the airstream is 58.8 W; the remaining 31.6 W is lost to friction and mechanical losses.
  • At 0.121 BHP this is a small fan, suitable for residential HVAC, electronics cooling, or bathroom ventilation.
  • Motor selection should add at least a 10-15% service factor above the calculated shaft power to handle startup loads and system variations.

Next stepSelect a motor rated at least 10-15% above the calculated shaft power, then verify with the fan curve at your system static pressure.

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