> What is bigger: a 400-pixel square or a 400-pixel circle? Geometrically speaking, their width and height are equal. The area of a circle isn't width * height

> What is bigger: a 400-pixel square or a 400-pixel circle? Geometrically speaking, their width and height are equal. The area of a circle isn't width * height though, obviously. If you plug pi * r^2 = 400^2 into WolframAlpha, you get a diameter of 2*r = 451.35 pixels, very close to the 450 pixels the author came up with. For the icons too, maybe you could just count the pixels (ask Photoshop the amount of filled in pixels?) and make sure every icon has a similar amount.