Actually, the easiest way would be to apply a "Tape Measure" and see how much larger the sump of the pan is than a stock one. If the pan is the same width then from the bottom of the front part of the pan (this varies because of the additional clearance needed for the stroker assembly) but the sump dimensions usually doesn't change much. However, if the sump is deeper than a stock one (Measuring from the bottom of the shallow part of the pan) then add a quart per inch. A stock SBC pan is 5 quarts in the sump, generally.
All this goes out the window when you start widening and lengthening the oil pans for a number of reasons, capacity, being one of them . .
Didn't mean to sound like a smart ass but you're just doing basic physics . . Y'know, that's the class we all slept through in High School because we were gearheads and were never gonna need that stuff . .