How to use this calculator
- Enter aircraft weight. Use loaded weight for the condition being checked.
- Enter wing area. Use the planform area from aircraft data.
- Set air density. Use standard sea-level density or a condition-specific density.
- Enter CLmax. Use the maximum lift coefficient for the configuration.
How it works
Stall begins when required lift coefficient reaches the maximum available value. Rearranging L = 0.5 x rho x V^2 x S x CL gives Vs = sqrt(2W / (rho x S x CLmax)).
Use the result with maneuvering speed, load factor and weight and balance.
Worked example
Verified against the live calculator
A 2,300 lb aircraft, 174 ft^2 wing, sea-level density and CLmax 1.5 gives an estimated stall speed of about 58 kt.
Frequently asked questions
What formula does the stall speed calculator use?
It uses Vs = sqrt(2W / (rho x S x CLmax)), where W is aircraft weight, rho is air density, S is wing area and CLmax is maximum lift coefficient.
Where do I get CLmax?
CLmax is aircraft- and configuration-specific. Use manufacturer, test or approved data when available.
Does this include flaps or landing gear?
Only if the CLmax you enter reflects that configuration. The calculator does not infer configuration changes.
Why is air density an input?
The lift equation depends on density. Lower density increases true-air-speed stall speed for the same weight and CLmax.
Method & assumptions
- Uses steady lift-equation physics with entered CLmax and density.
- Does not model CG, propwash, contamination, position error, buffet margin or certified stall-speed definitions.