Calculating the ratio between any two variables is so simple that you just need to divide the one variable by the other. The below given is the Protein creatinine ratio formula to calculate the urine protein-creatinine ratio (PCR) for the given values. The Protein-Creatinine Ratio PCR can be calculated just by dividing protein with the creatinine. Protein and creatinine are to be given in the mg/dL and the ratio of protein-to-creatinine output will be in mg/g.