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Free static pressure and airflow check for HVAC

Type the two static readings from your manometer and get total external static pressure (TESP) against the furnace data plate. Add temperatures and BTU output for temperature rise and an airflow estimate. Free, no signup, and it keeps working with no signal once the page is open.

1. Total external static pressure

Either sign works. The calculator uses the absolute values, so you can skip the minus on a phone keypad.

Enter both readings to see the result.

2. Temperature rise (optional)
3. Estimated airflow (optional)

Needs the BTU output and a temperature rise above zero.

A quick field check for trained technicians. Always follow the manufacturer's installation instructions, blower data and local codes. Terms.

How to take the readings

  • Drill the test ports
    Use a small hole in the plenum or duct, away from elbows and transitions. Plug it with a rubber or metal plug afterward.
  • Supply static
    Between the furnace and the coil, or after the coil, depending on the manufacturer. Check the install manual for the spot it wants.
  • Return static
    Between the filter and the blower, on the return side.
  • Let it settle
    Run the blower at the speed you will leave it on, with the filter in and the system in steady state, then read both.
  • Temperature rise
    Measure return air and supply air temperature in the furnace airstream, in heating mode after a few minutes of steady burn.

Keep every unit's data plate on your phone

Get HVAC Pad keeps each unit's data plate and service history with the customer, and it works with no signal.

See how it works

Static pressure questions

What is total external static pressure?

It is the pressure the blower works against outside the furnace or air handler: the supply static plus the return static, each taken as a positive number. It is measured in inches of water column (in. w.c.).

What is a normal static pressure?

Check the data plate. Many furnaces list a maximum external static pressure such as 0.5 in. w.c. for heating. Staying at or under the plate value is the goal.

Why does the calculator use absolute values?

The return side reads negative on a manometer, and phone keypads often have no minus key. Total external static adds the two sizes, so the sign does not matter here.

What temperature rise should I see?

Whatever the data plate says, for example 25 to 55 °F. A rise outside that range points to an airflow or firing problem.

How accurate is the airflow number?

It is an estimate from the sensible heat formula at sea level. Use the manufacturer's blower table with your static reading for the real figure.

Does this send my readings anywhere?

No. The maths runs in your browser and nothing is sent or saved.