It depends on what you're really looking for. If you want to find what percent of x (denominator) is y (numerator), then do 100*y/x.  Example: 100 * 20 / 80 = 25 (25% of 80 is 20). The other way around: Denominator = 100 * numerator / percentage.  80 = 100 * 20 / 25. … Read more