The algorithms used for the tool above are the exact same as published by:

Cockcroft DW, Gault MH.: Prediction of creatinine clearance from serum creatinine. Nephron 1976;16:31-41. Abstract link 

Levey AS, Bosch JP, Lewis JB, Greene T, Rogers N, Roth D.: A more accurate method to estimate glomerular filtration rate from serum creatinine: A new prediction equation. Ann Intern Med 1999;130:461-470. Abstract link | Full text PDF

Updated: 08 Dec 2006