Measure them? I do know that the longer the arms are, the easier a deadlift will be, but the harder a bench press will be. Because in the bench you have to push the bar over a longer path of resistance.
Most people are average, people with shorter limbs put on muscle faster and easier than people with long limbs. But people with long limbs look better once they add muscle and fill out.
No joke here, there is a dude down at the watering hole that when he holds his arms straight down, his finger tips touch his belt. When he gets mad and throws a hissy fit, he looks like a T-Rex swatting away flies with his little limbs.
Then again, I used to watch the late Eddie Guerro when he wrestled and couldn't help but to think he could tie his shoes without bending over. His arms were dangly long. But when he hit the sauce and they blew up, they looked great.