Fan Laws Calculator

Calculate how changes in fan speed affect airflow, pressure, and power consumption.

Operation Parameters

Initial Speed (RPM)

Target Speed (RPM)

Initial Flow (CFM)

Initial Pressure (in wg)

Initial Power (HP)

New Fan Performance

Enter speed and performance data

About this calculator

Quick Reference

RPMRevolutions Per Minute

CFMCubic Feet per Minute

in wgInches Water Gauge (static pressure)

HPHorsepower

Overview

Fan laws (or Affinity Laws) are a set of formulas used to predict the performance of a fan or blower at different speeds or sizes.

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Pro Tips

Fun Facts

"The Fan Laws work best for centrifugal and axial fans where air density remains constant."
"A small increase in speed can lead to a massive increase in energy costs due to the cubic power law."
"These laws also apply to pumps, where they are known as Pump Laws."

Formula: Flow ∝ RPM, Pressure ∝ RPM², Power ∝ RPM³