This GFR calculator determines the glomerular filtration rate based on serum creatinine, patient age, gender and race. GFR is the most important of the parameters that evaluate kidney function. It is estimated through different methods based on serum creatinine. Creatinine is the break down product of the creatinine phosphate, involved in muscular function. Serum creatinine levels determine the clearance that is used further on to establish GFR. GFR offers information on the amount of liquid that gets filtered by the capillaries of the kidney glomerular into the Bowman's capsule during a specific time period. Thus, its value shows how efficiently the kidneys perform their function, that of cleaning blood of different waste products and toxins and their excretion through urine. Glomerular filtration rate can be physically determined by comparing concentrations of a marker substance in a sample of blood an in a sample of urine. GFR formulas The above calculator employs the following formulas to determine the glomerular filtration rate: The IDMS-traceable MDRD equation: GFR = 175 x (SCr)-1.154 x (Age)-0.203 x (0.742 only if female) x (1.212 only if black) The CKD-EPI formula is composed based on patient gender and race, as presented in the following table: Race Gender Serum Creatinine (SCr) Formula (GFR = ) White/ Other race Female 0.7 144 x (SCr/0.7)-0.329 x 0.993Age >0.7 144 x (SCr/0.7)-1.209 x 0.993Age Male 0.9 141 x (SCr/0.9)-0.411 x 0.993Age >0.9 141 x (SCr/0.9)-1.209 x 0.993Age Black Female 0.7 166 x (SCr/0.7)-0.329 x 0.993Age >0.7 166 x (SCr/0.7)-1.209 x 0.993Age Male 0.9 163 x (SCr/0.9)-0.411 x 0.993Age >0.9 163 x (SCr/0.9)-1.209 x 0.993Age The Mayo Quadratic formula: GFR = e^(1.911 + 5.249/SCr - 2.114/SCr2 - 0.00686 x Age - (0.205 only if Female)) Where: e = 2.71828182845905 SCr = the serum creatinine, either expressed in mg/dL. When SCr is expressed in mol/L, the conversion rate that should be used is 88.4 mol/L = 1 mg/dL. Note that in any case serum creatinine is less than 0.8 mg/dL, the Mayo Quadratic Formula uses 0.8 mg/dL default for SCr. In the case of pediatric patients, the Schwartz formula is used: GFR = 0.41 x Height (in cm) / SCr The optimal GFR level is around 60 mL/min/1.73 m2 level. The table below summarises the chronic kidney disease stages and their associated glomerular filtration rates: CKD stage GFR level (mL/min/1.73 m2) Other observations 0 Stage - Normal kidney function 90 No proteinuria 1st Stage 90 Kidney damage signs 2nd Stage 60 89 Mild 3rd Stage 30 59 Moderate 4th Stage 15 29 Severe 5th Stage <15 Kidney Failure