Industrial Fans, Blowers & Air Movement Equipment worked example

Motor Sizing with design airflow of 6,000 CFM: a worked example in industrial fans, blowers & air movement equipment

Here is what the math looks like when conditions slip. We hold every other input steady and drop design airflow to 6,000 CFM, then walk the calculation through step by step. Estimate fan motor sizing from airflow, static pressure, a power conversion basis, and service factor.

The inputs for this scenario

  • Design airflow: 6,000 CFM (the input this scenario stresses; the baseline uses 12,000)
  • Design static pressure: 6 in. w.c. (held at the documented default)
  • Power conversion basis: 0 hp / CFM-in. w.c. (held at the documented default)
  • Motor service factor or sizing margin: 1.15 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Estimated motor size = design airflow × design static pressure × power conversion basis × motor service factor or sizing margin.
  • Result works out to 9.11 hp at these inputs, and this is the headline figure for the scenario.
  • Base product works out to 7.92 value at these inputs.
  • Multiplier works out to 1.15 x at these inputs.
  • Factor A x B works out to 36,000 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where design airflow sits at 12,000 CFM and the headline result is 18.22 hp, this scenario comes in 50% below the baseline at 9.11 hp.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to design airflow, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. The single conversion basis bakes in an assumed fan and drive efficiency, so it cannot capture how efficiency shifts along the fan curve and should never replace a manufacturer's brake horsepower selection.

Results at a glance

  • Result: 9.11 hp (headline result)
  • Base product: 7.92 value
  • Multiplier: 1.15 x
  • Factor A x B: 36,000 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Motor Sizing calculator, set design airflow to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.