eGFR calculator

What is eGFR?

Estimated glomerular filtration rate — how much blood the kidneys filter per minute, adjusted to body size and calculated from a blood creatinine test. It is reported in mL/min/1.73 m².

Which equation does this use?

The 2021 CKD-EPI creatinine equation, which does not use race and is the one recommended by the National Kidney Foundation. A 50-year-old man with a creatinine of 1.0 mg/dL has an eGFR of about 92.

What do the eGFR categories mean?

KDIGO groups eGFR as G1 (90 or more, normal or high), G2 (60–89), G3a (45–59), G3b (30–44), G4 (15–29) and G5 (under 15, kidney failure).

Does a normal eGFR mean healthy kidneys?

Not by itself. G1 or G2 counts as chronic kidney disease only with other signs of kidney damage, such as protein in the urine.

My lab reports creatinine in µmol/L — can I use it?

Yes, switch the unit. 1 mg/dL is 88.4 µmol/L.

How does the CKD-EPI 2021 equation work?

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age, multiplied by 1.012 for women. Scr is serum creatinine in mg/dL, κ is 0.7 for women and 0.9 for men, and α is −0.241 for women and −0.302 for men. The min and max terms make the curve bend at κ: below it creatinine barely changes the result, above it each rise lowers the result steeply. The equation was developed by Inker and colleagues (New England Journal of Medicine, 2021) from 10 studies with 8,254 participants and checked in 12 other studies with 4,050 participants. For all the equations tested, at least 85% of estimates were within 30% of the measured GFR.

Worked example: a 62-year-old woman with a creatinine of 1.1 mg/dL

Divide the creatinine by κ = 0.7: 1.1 ÷ 0.7 = 1.57. Because that is above 1, the max term applies: 1.57^−1.200, and the min term equals 1. Multiply by 142, by 0.9938^62 for age, and by 1.012 for sex. The result is 56.8 mL/min/1.73 m², which falls in category G3a (mildly to moderately decreased). By itself this does not diagnose kidney disease: that depends on other findings, such as protein in the urine.

How precise is an eGFR?

It is an estimate from a blood level, not a measured filtration rate. The NIDDK notes that most estimating equations become less accurate as GFR increases, so the difference between 95 and 105 means little, and that using both creatinine and cystatin C gives higher accuracy and less bias than creatinine alone. Ask your clinician whether a cystatin C test would help in your situation.

Common mistakes with eGFR

Entering creatinine in µmol/L as if it were mg/dL: a value of 88 µmol/L typed as 88 mg/dL gives 0.3 mL/min/1.73 m², a result near zero, instead of about 57. Using an adult equation for a child: the NIDDK’s adult calculator applies to ages 18 and older, with separate pediatric equations. Comparing eGFR with a drug-dosing creatinine clearance: eGFR is scaled to 1.73 m² of body surface, while the Cockcroft-Gault clearance is in plain mL/min, so the two numbers can differ for a very large or small person. Looking for a race term: the 2021 equation has none, so an older report calculated with a race coefficient may not match today’s result.

Sources and related calculators

Sources: L. A. Inker et al., “New creatinine- and cystatin C-based equations to estimate GFR without race,” New England Journal of Medicine (2021); National Kidney Foundation, “How to Classify CKD” (KDIGO GFR and albuminuria categories); NIDDK, glomerular filtration rate pages for health professionals. Related: creatinine clearance calculator, body surface area calculator and blood pressure calculator.

For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.