I see it being used interchangeably (for example by Airfoil Tools Fusion360 AddIn), so can I just pick an airfoil from the airfoiltools database with a certain CL/CD for my aircraft and assume L/D is the same?
An example airfoil from the database: clarky-il
(I know there is induced drag as well, which is not calculated in the databse)

I know the formulas, so it makes sense to me. Just want to verify there is not something I am not aware of, in case I want to calculate the lift depending on the angle of attack.


1 Answer 1


Yes. Lift and Drag are both obtained by multiplying the CL & CD by the same factors (1/2 rho V^2 S); the ratio L/D cancels out those factors, leaving CL/CD.

  • $\begingroup$ I thought a bit more about it and now it seems so obvious. Thanks for verifying it. $\endgroup$
    – RIJIK
    Oct 11, 2020 at 8:21

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