Allen day has the correct answer

There is no approximated mathematical number or eqation that has the ability of measuring wounding effect of a projectile.

What we can do is to model and predict how a projectile behaves in the target, what we cannot do however is to predict how that behaviour would effect the animal or person you are shooting.

The various stopping and knock down formulae are just formulae and do not in any way represent wounding capability as none of them take projectile path and target physiological and psychological reserve into account.