And getting actual size on a display is tricky, because most displays don't accurately report the pixels per inch that they display (so "actual size" is approximate unless you calibrate the display size).
it's fabric patterns i work for a textile mill and usually just take pictures but i couldn't figure this out. i've been looking online and a lot ppl say its not possible because all monitors are different
I do some measured printed proofs to compare with screen. Mine runs close to true at somewhere around 33%. Compare your screen to a print and not size at dpi. For clients to see approx I do screen shots once I've determined approx size.