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Calcimator

Fan Selection Calculator

Select an HVAC or industrial fan by calculating brake horsepower, motor size, estimated tip speed, noise level, and annual energy consumption.

Inputs

CFM
in. WG
%
%

Results

Brake Horsepower

2.25 HP

≈ 28 laptops

Motor Size

3 HP

≈ 2 microwaves

Estimated Tip Speed7,540 ft/min
Noise Estimate61 dB
Annual Energy Use16,320 kWh
How to Use This Calculator
  1. Enter the required Airflow Rate in CFM based on ventilation or process load calculations.
  2. Enter the total Static Pressure in in. WG — sum ductwork friction, filter loss, and fitting losses for the system curve.
  3. Set the Fan Efficiency: forward-curved blades ≈ 60–70%, backward-curved ≈ 75–85%, airfoil ≈ 80–90%.
  4. Set the Motor Efficiency: standard efficiency motors ≈ 85–90%, premium efficiency ≈ 92–96%.
  5. Read the Brake Horsepower and the recommended Motor Size (next standard HP above BHP).
  6. Review the Annual Energy Use in kWh to evaluate lifecycle operating cost for the selected fan.

How the result changes with Fan Efficiency

Fan EfficiencyBrake HorsepowerMotor Size
374.25 HP5 HP
532.97 HP3 HP
722.19 HP3 HP
891.77 HP2 HP

What each input means

Airflow Rate
Required airflow in cubic feet per minute based on ventilation or process requirements.
Static Pressure
Total system static pressure the fan must overcome, in inches water gauge. Sum of ductwork, filters, and fittings losses.
Fan Efficiency
Total fan efficiency. Forward-curved ≈ 60-70%; backward-curved ≈ 75-85%; airfoil ≈ 80-90%.
Motor Efficiency
Motor efficiency. Standard efficiency ≈ 85-90%; premium efficiency ≈ 92-96%.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Airflow Rate = 5000, Static Pressure = 2, Fan Efficiency = 70, Motor Efficiency = 90 = 4 input(s) provided
  2. Calculate Brake Horsepower
    Brake Horsepower
    2.25 = 2.25
  3. Calculate Motor Size
    Motor Size
    3 = 3
  4. Calculate Estimated Tip Speed
    Estimated Tip Speed
    7540 = 7540
  5. Calculate Noise Estimate
    Noise Estimate
    61 = 61

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