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Calculation Machine

Static Pressure Calculator

Total external static pressure health check.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Total external static
0.78 in w.c.
Percent of blower rating
156%
Dominant restriction
supply side
In pascals
194
Verdict
Over rating — airflow and capacity are suffering

Quick answer

Total external static pressure is the supply reading plus the absolute value of the return reading, and should stay at or under the blower's rating, usually 0.5 in w.c.

The formula

TESP = supply static + |return static|

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Supply static0.42 in w.c.
  • Return static0.36 in w.c.
  • Blower rated static0.5 in w.c.

Result

  • Total external static0.78 in w.c.
  • Percent of blower rating156%
  • Dominant restrictionsupply side
  • In pascals194
  • VerdictOver rating — airflow and capacity are suffering

How to use the Static Pressure Calculator

  1. 1Drill test ports upstream and downstream of the air handler.
  2. 2Record the supply and return readings with a manometer.
  3. 3Enter the blower's rated static from the data plate.

Frequently asked questions

What is a good static pressure?

0.5 in w.c. or less total on most residential equipment; many real systems measure 0.8 or worse.

What causes high static?

Undersized returns, dirty filters, crushed flex duct and restrictive coils are the usual culprits.

About this calculator