I guess a better way to write this is diagonal <= 0.000275774245 * sqrt(horizontal resolution^2 + vertical resolution^2) * viewing distance Edit: Wow, somethi

I guess a better way to write this is diagonal <= 0.000275774245 * sqrt(horizontal resolution^2 + vertical resolution^2) * viewing distance Edit: Wow, something interesting came up when I was playing with the numbers. If you assume iPad 3 resolution and iPhone 4 viewing distance the diagonal comes out to 7.8" inches.