Duct Leakage Test Calculator

Evaluate duct leakage rates against SMACNA seal class standards

The static pressure at which the duct leakage test is conducted. Typically 1.0 in.wg for low-pressure systems, up to 6.0 for high-pressure.
in.wg
Total airflow leakage measured during the pressurization test using a calibrated fan or orifice plate.
CFM
Total exterior surface area of the duct section being tested. Calculate from duct dimensions and length.
sq ft
SMACNA seal class: A (most stringent, all seams/joints sealed), B (transverse joints and seams), C (transverse joints only).

Results

Leakage RateCFM/100sqft
Max Allowable LeakageCFM/100sqft
Test Result
Energy Loss Estimate%
Recommendation
References: SMACNA HVAC Duct Leakage Test Manual, ASHRAE 90.1 duct sealing requirements. Class A allows 4 CFM/100sqft at 1 in.wg, Class B allows 12, Class C allows 24.