eGFR Calculator (CKD-EPI 2021)

Understanding the eGFR calculator (CKD-EPI 2021) — concept and principle

eGFR, the estimated glomerular filtration rate, shows how much blood your kidneys filter per minute, scaled to a standard body surface area of 1.73 m². This calculator uses the 2021 CKD-EPI creatinine equation, which no longer includes a race term, and places the result in a KDIGO GFR category. Doctors use it to detect and stage chronic kidney disease and to adjust drug doses.

Creatinine and age each shrink the starting 142 a little; here the result is about 101.

How it is calculated

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (if female)

Scr is serum creatinine in mg/dL.
κ = 0.7 for women and 0.9 for men; α = −0.241 for women and −0.302 for men.
The result is in mL/min/1.73 m².

The principle

Creatinine is a waste product of muscle that is made at a fairly steady rate and removed almost entirely by kidney filtration. When filtration falls, creatinine builds up in the blood, so GFR is roughly inversely related to creatinine. The equation fits this curve with two slopes: a gentle one below the typical creatinine level κ and a steeper one above it. Age and sex terms account for average differences in muscle mass. The coefficients were fitted to thousands of people whose GFR was measured directly with filtration markers.

Worked example

Inputs: male, age 35, creatinine 1.0 mg/dL; so κ = 0.9 and α = −0.302.
Scr/κ = 1.0 ÷ 0.9 = 1.111. The min term is 1, so 1^α = 1.
Max term: 1.111^−1.2 = 0.8812.
Age term: 0.9938^35 = 0.8044.
eGFR = 142 × 1 × 0.8812 × 0.8044 = 100.66, shown as 101, category G1 (normal or high).

Each point is the calculator re-run with only “Serum creatinine (mg/dL)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Serum creatinine (mg/dL)	eGFR (mL/min/1.73 m²)
0.25	168
0.5	136
0.75	121
1	101
1.25	77
1.5	62
2	44

How to read the result

Where does your result fall?

KDIGO categories are G1 ≥ 90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29 and G5 below 15. Chronic kidney disease is diagnosed only when GFR stays below 60 for more than three months, or when there are signs of kidney damage such as albumin in the urine; a G1 or G2 value alone is not a disease. GFR declines gradually with age, so values in the 70s or 80s are common in older adults.

Common mistakes

Using creatinine in µmol/L; divide by 88.4 to get mg/dL first.
Applying the equation during sudden kidney injury, when creatinine has not yet stabilised.
Ignoring body build: very muscular people may get a falsely low eGFR, and people with very low muscle mass a falsely high one.

Keep in mind: eGFR is an estimate and is less reliable at extremes of muscle mass, in pregnancy and in children. This is not a diagnosis; a doctor may confirm with cystatin C or a urine albumin test.

Frequently asked questions

Why was race removed from the equation?

The 2021 revision dropped the race coefficient because race is a social, not biological, category and the adjustment could delay diagnosis; the refit equation performs similarly across groups.

Can I raise my eGFR?

A single reading can vary with hydration, recent meat intake and exercise. Long-term, controlling blood pressure and blood glucose helps protect kidney function.

Is eGFR the same as creatinine clearance?

No. Creatinine clearance (Cockcroft-Gault) is in mL/min without body-size scaling and is still used for some drug dosing.

Sources: Inker LA et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med 2021;385:1737–1749. · KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.

Checked 8 Nov 2026. Inker et al., NEJM 2021; KDIGO 2012 staging.

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