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Static Pressure Tool · Free Calculator

Static Pressure
Calculator

Calculate total external static pressure and diagnose airflow restrictions. Compare measured vs. design to find problems.

Understanding Static Pressure

Static pressure is the resistance to airflow in your duct system, measured in inches of water column (in. WC). It's the most important diagnostic measurement in HVAC — high static pressure means your system is working harder than designed, reducing efficiency and lifespan.

What Causes High Static Pressure?

Dirty filters, undersized ductwork, closed dampers, collapsed flex duct, and blocked return grilles are the most common causes. A dirty filter alone can increase static by 0.2-0.4" WC, reducing airflow by 20-30%. Replace filters regularly and keep blower motors clean.

Frequently Asked Questions

What should static pressure be in HVAC?
Total external static pressure should be at or below the equipment's rated capacity, typically 0.50" WC for residential systems. Ideal is 0.30-0.40" WC total.
What happens when static pressure is too high?
Low airflow, frozen evaporator coils, short-cycling, high energy bills, and premature blower motor failure. The motor works harder to push air through the restriction.

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