Ironically, the MOA setup runs identically to the MRAD version just in inches. 1 MOA is roughly 1" at 100yds, 2" at 200 etc although it's not quite as accurate (MOA not quite being inches).
As long as you know what the scope is set up for, the reticle if it's got aiming marks or whatever matches the scope's adjustments and you know what power they are correct on if the scope is SFP (second focal plane) or if there isn't a power that the scope is set up for you know what the mark's distance is at at each power you can scratch through.
Where it turns into a brain fluck is where you hit a scope that adjusts in MOA but the reticle is in mildots. That can hurt your brain...
