Calculators for similar things have been developed.
But factors such as your personal preference to tightening, and the elasticity of the material used, will speak for the method of tying a defined length, then measure the used goods. Add a bit to pull with when you come to the end. And don't be shy with it.
Sometimes, such as with the French sinnet, the start differs from the run slightly, and it could be wise to make different tests.
Keep a log of your experiences!