How heavy should polyurethane be applied?

Q: How heavy should polyurethane be applied?

A: Most finishes are to be applied at a spread rate of

500 sq. ft. per gallon.

Related Q: How thick is the seal coat used on my wood floors when using a 1/2 gallon of sealer to cover 400 sq. ft of wood flooring? Is their a formula I can use?

A: I know there is a formula, but can’t find the information on it at the moment. It is somewhat theoretical though because it involves the amount of solids in the coating (the higher solids content, the thicker the film) and having it applied at the recommended spread rate, which more often than not is 500 sq. feet per gallon.