Kidney Glomerular Filtration Rate eGFR Calculator
Implements 5 following calculation formulas :
1. CKD-EPI 2009 Formula ( recommended by Kidney foundation )
2. MDRD Formula
3. Mayo Quadratic Formula
4. Cockroft-Gault Formula
5. Scwartz ( pediatric, for children ) Formula

Details on calculation formulas:

1. CKD-EPI 2009 Formula ( Chronic Kidney Disease Epidemiology Collaboration )
eGFR = 141 X min(SCr/k,1)^a X max(SCr/k,1)^(-1.209) X 0.993^Age X [1.018 if Female] X [1.159 if Black]
where SCr is serum creatinine (mg/dL),
k is 0.7 for females and 0.9 for males,
a is 0.329 for females and 0.411 for males,
min indicates the minimum of SCr/k or 1,
and max indicates the maximum of SCr/k or 1,
eGFR - estimate the glomerular filtration rate.


2. MDRD Formula ( Modification of Diet in Renal Disease )
For creatinine in µmol/L:
eGFR = 32788 X Serum Creatinine^(-1.154) X Age^(-0.203) X [1.210 if Black] X [0.742 if Female]
For creatinine in mg/dL:
eGFR = 186 X Serum Creatinine^(-1.154) X Age^(-0.203) X [1.210 if Black ] X [0.742 if Female]
where:
eGFR - estimate the glomerular filtration rate

3. Mayo Quadratic Formula
eGFR = exp(1.911 + 5.249/Serum Creatinine - 2.114/Serum Creatinine^2 - 0.00686 X Age - [0.205 if Female] )
If Serum Creatinine < 0.8 mg/dL, use 0.8 mg/dL for Serum Creatinine.

4. Cockroft-Gault Formula
eCCr = ( (140 - Age) X Mass ( in kilograms) X [0.85 if Female] ) / 72 X Serum creatinine ( in mg/dL )
When serum creatinine is measured in µmol/L:
eCCr = ( 140 - Age ) X Mass ( in kilograms ) X Constant
where :
eCCr - estimated creatinine clearance rate,
Constant is 1.23 for men and 1.04 for women.


5. Scwartz ( pediatric, for children ) Formula
eGFR = k X Height / Serum Creatinine
Where k is a constant that depends on muscle mass, which itself varies with a child's age:
In first year of life, for pre-term babies k=0.33 and for full-term infants k=0.45
For infants and children of age 1 to 12 years, k=0.55.
eGFR - estimate the glomerular filtration rate.

Chronic kidney disease stages:
0) Normal kidney function – GFR above 90 mL/min/1.73 m2 and no proteinuria
1) CKD1 – GFR above 90 mL/min/1.73 m2 with evidence of kidney damage
2) CKD2 (mild) – GFR of 60 to 89 mL/min/1.73 m2 with evidence of kidney damage
3) CKD3 (moderate) – GFR of 30 to 59 mL/min/1.73 m2
4) CKD4 (severe) – GFR of 15 to 29 mL/min/1.73 m2
5) CKD5 kidney failure – GFR less than 15 mL/min/1.73 m2.
Some people add CKD5D for those stage 5 patients requiring dialysis;
many patients in CKD5 are not yet on dialysis.

Information source : https://en.wikipedia.org/wiki/Renal_function