The Fan Law Calculator App has been designed to allow quick estimation of the performance impact of variation in airflow and/or rpm on an existing system. The standard fan law equations are used to estimate the system performance changes.

Input the current values for airflow, rpm, pressure and current (or power) into the appropriate text field. The calculations will automatically update as you type.

The updated values can be input in one of two ways. The new values can be entered into the appropriate text field. Or, you can drag the airflow value left and right on the graph view to change the values. The calculations will automatically update as you edit the values.


The standard fan law equations are applied:
cfm2 = cfm1 * rpm2/rpm1
sp2 = sp1 * (cfm2/cfm1)^2
power2 = power1 * (cfm2/cfm1)^3

This application (App) is provided for use by qualified HVAC engineers and designers in the design of air handling systems and is not a substitute for appropriate design services. When in doubt, contact a design

What’s New

Version 1.1

• iOS 13 updates
• Dark mode

Ratings and Reviews

4.5 out of 5
2 Ratings

2 Ratings

App Privacy

The developer, Pheinex, LLC, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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