5x4 Bolt Pattern Aftermarket Options

I can never remember which is positive offset, and which is negative. Plus, if you don't know the width of a wheel (cause it has a tire on it, for instance) an offset number tells you nothing, and CANT be measured. Therefor, i dont even try to deal with offset.
Any wheel, tire on it or not, can be measured for backspace. And you dont need to know the width. Example: if i told you i have a fairly wide wheel with a +37 offset, will it fit your car? I would have no clue. But (the SAME wheel) tell me that fairly wide wheel has 7 1/4" of backspace, I'll KNOW if it will fit or not. (Above wheel exists, in my garage. It is intended for an A-body with a stock A or B body width rear in a car with moved springs, and that's about all it will fit, lol)