Total External Static Pressure Calculator
TESP from supply and return readings.
Enter your values
ⓘ Live results
Results
- Total external static
- 0.8 in wc
- Rated maximum
- 0.5 in wc
- Percent of rating
- 160%
- Verdict
- Over — airflow and efficiency are suffering
- Worse side
- Supply duct
Quick answer
Total external static pressure is the supply-side positive reading plus the absolute value of the return-side negative reading.
TESP = supply + |return|
How to use the Total External Static Pressure Calculator
- 1Drill test ports right at the air handler, outside the coil and filter.
- 2Record supply as positive and return as negative, then enter both.
- 3Compare against the blower's rated maximum, usually 0.5 in wc.
Worked example
Using the values the calculator loads with:
Inputs
- Supply static0.42 in wc
- Return static0.38 in wc
- Equipment rating0.5 in wc
Results
- Total external static0.8 in wc
- Rated maximum0.5 in wc
- Percent of rating160%
- VerdictOver — airflow and efficiency are suffering
- Worse sideSupply duct
Frequently asked questions
Why is high static bad?
The blower moves less air, coils freeze or overheat, and energy use climbs.
Common cause?
Undersized return duct and restrictive high-MERV filters top the list.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.