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Airflow Measurement Calculator

Calculate CFM from field measurements using various ASHRAE-approved methods.

Velocity Method

Corrections (Optional)

Measurement Methods

MethodAccuracyApplication
Capture Hood+/-3%Diffusers, grilles
Pitot Traverse+/-5%Duct measurement
Hot Wire+/-3%Low velocity
Ak Factor+/-10%Quick estimate

Formulas

CFM = Velocity (FPM) x Area (sq ft)

Velocity = 4005 x sqrt(VP / density)

Standard density = 0.075 lb/ft3 @ 70F, sea level