eGFR Calculator
Estimate kidney function with the race-free CKD-EPI 2021 creatinine equation plus Cockcroft-Gault clearance, with µmol/L switching and KDIGO staging.
CKD-EPI 2021 creatinine eGFR
89 mL/min/1.73 m²
142 × min(1.00/0.90, 1)^−0.302 × max(…, 1)^−1.200 × 0.9938^55 = 88.9
Both equations side by side
| Equation | Result | What it is for |
|---|---|---|
| CKD-EPI 2021 creatinine | 88.9 mL/min/1.73 m² | The equation KDIGO and most labs now report. Race-free since 2021. Indexed to a standard 1.73 m² body surface area, so it is a population comparison, not your literal filtration rate. |
| Absolute (de-indexed) eGFR | 98.1 mL/min | eGFR × your body surface area ÷ 1.73, using the Mosteller BSA (1.91 m²). Some drug-dosing references want this rather than the indexed figure. |
| Cockcroft-Gault creatinine clearance | 88.5 mL/min | From 1976 and still the basis of many drug licences and renal dosing tables. Uses actual body weight of 75.0 kg. It over-estimates GFR because creatinine is secreted as well as filtered. |
Worked check: a 50-year-old man with a creatinine of 0.9 mg/dL gives 142 × 1 × 1 × 0.9938⁵⁰ = 104 mL/min/1.73 m², which matches the National Kidney Foundation's own calculator. Creatinine converts at 88.4 µmol/L per mg/dL.
An educational estimate, not a diagnosis and not medical advice — never use it to choose or adjust a drug dose. Creatinine-based equations assume a steady state, so they are unreliable in acute kidney injury, and they are skewed by muscle mass, amputation, pregnancy, a very high or very low protein intake, creatine supplements, and drugs such as trimethoprim and cimetidine that block creatinine secretion without changing filtration. Roughly one estimate in ten falls more than 30% away from a measured GFR. Chronic kidney disease is defined by KDIGO from both GFR and albuminuria over at least three months, not from a single number. Discuss any result with your doctor.
What is the eGFR Calculator?
The CKD-EPI 2021 creatinine equation estimates GFR as 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × 1.012 if female, where κ is 0.7 for women and 0.9 for men and α is −0.241 and −0.302 respectively.
- CKD-EPI 2021 creatinine equation, race-free, with the working shown
- KDIGO G1 to G5 staging with a plain-English explanation of each band
- Cockcroft-Gault creatinine clearance with actual, Devine ideal or adjusted body weight
- Absolute de-indexed eGFR in mL/min using Mosteller body surface area
- mg/dL and µmol/L entry with automatic conversion at 88.4 µmol/L per mg/dL
- Runs entirely offline in your browser — no lab values are uploaded
How to use the eGFR Calculator
- 1
Select mg/dL or µmol/L and enter the serum creatinine from your lab report.
- 2
Enter age in years and select sex — the 2021 equation keeps a sex coefficient but has removed the race coefficient.
- 3
Add weight, and height if you have it, to enable Cockcroft-Gault and the de-indexed absolute eGFR.
- 4
Choose whether Cockcroft-Gault should use actual, Devine ideal or adjusted body weight.
- 5
Read the eGFR headline with its KDIGO stage badge, then compare all three equations in the table below.
About the eGFR Calculator
The ByteTools eGFR Calculator implements the CKD-EPI 2021 creatinine equation — the race-free version that KDIGO and most laboratories now use — and reports the result with its KDIGO stage from G1 through G5. Enter a serum creatinine in mg/dL or µmol/L along with age and sex, and you get the estimate plus the exact arithmetic behind it.
Because renal drug dosing tables are often still written around the older equation, Cockcroft-Gault creatinine clearance is calculated alongside, with a choice of actual, Devine ideal or adjusted body weight. Adding height also produces a Mosteller body surface area and a de-indexed absolute eGFR in mL/min, which is what some dosing references actually want.
Everything is computed in your browser and nothing is uploaded. This is an educational estimate, not a diagnosis and not medical advice, and it must never be used to choose or adjust a drug dose. Creatinine-based equations assume a steady state and are skewed by muscle mass, amputation, pregnancy and several common medications. Discuss any result with your doctor.
Frequently asked questions
What is a normal eGFR?
An eGFR of 90 mL/min/1.73 m² or above is classed G1 (normal or high), and 60 to 89 is G2 (mildly decreased). Neither is chronic kidney disease on its own — a diagnosis needs either a GFR below 60 or evidence of kidney damage such as albuminuria, sustained for at least three months.
What is the CKD-EPI 2021 equation?
It is the current creatinine-based estimate published by Inker and colleagues in the New England Journal of Medicine in 2021: 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age, multiplied by 1.012 for women. Its headline change was removing the race coefficient that earlier versions applied to Black patients.
Why did they remove race from the eGFR equation?
The old coefficient raised the reported eGFR for Black patients by about 16%, which could delay referral, transplant listing and specialist care. A joint NKF-ASN task force concluded that race is a social rather than biological variable and recommended an equation that does not use it — the 2021 version is the result.
What is the difference between eGFR and creatinine clearance?
eGFR estimates glomerular filtration rate indexed to a standard 1.73 m² body surface area, so it compares you to a population. Cockcroft-Gault estimates creatinine clearance in raw mL/min using your actual weight, and over-estimates true GFR because creatinine is secreted by the tubules as well as filtered. Many drug licences are still written around Cockcroft-Gault.
How accurate is an eGFR estimate?
Roughly one estimate in ten falls more than 30% away from a measured GFR. Muscle mass is the big confounder — a bodybuilder and an amputee with the same creatinine have very different kidney function — and creatine supplements, a very high protein intake, and drugs such as trimethoprim and cimetidine all shift creatinine without changing filtration.
Can children use this calculator?
No. CKD-EPI 2021 is validated in adults only, which is why the tool requires an age of 18 or over. Paediatric estimates use a different equation, usually the Bedside Schwartz formula, which factors in height rather than age and sex.
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