Friction Rate Calculator

Calculate available static pressure and friction rate from total external static pressure, component losses, and total effective length (TEL).

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Frequently asked questions

What is friction rate in duct design?

Friction rate is the allowable pressure loss per 100 feet of effective duct length, usually expressed in inches of water column per 100 feet. It is used with duct sizing charts and Manual D style methods.

How do you calculate available static pressure?

Available static pressure is calculated by subtracting filter, coil or equipment, and other known losses from total external static pressure. The result is the pressure left for the duct system.

What is total effective length (TEL)?

Total effective length is the resistance length of the duct path, including straight duct plus fittings converted into equivalent feet. It is used to estimate how pressure is distributed through the system.

Is this a full Manual D calculator?

No. This tool calculates available static pressure and friction rate to support duct sizing decisions. A full Manual D process also includes fitting values, airflow targets, duct layout, room-by-room analysis, and system verification.

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