To find the legnths from a diagonal, use Pythagorean theorem: aÂ² + bÂ² = cÂ² (c is the diagonal, a and b are the sides). 1Â² + 1.85Â² = xÂ². x = 2.1. Whatever diagonal you have, divide by 2.1. Use that to multiply by 1 and 1.85 to get respective height and width. In this case 88x48 as stated correctly above.