It is hard to do with Holley jets since the jet size isn't the same as the hole size. So with Holley jets you first have to figure out the hole size and then find the area.

I think the easiest way to do it is look at the conversion charts that BLP or MaxJet have. I just switched over to BLP jets since the size is the same as the number. That makes it a lot easier to compare area. You just compare the square of the number.