eGFR Calculator (Kidney Function)
Estimate how well your kidneys filter from a blood creatinine result, your age and sex, and see your kidney function stage in plain words.
Called “serum creatinine” on your lab report. US labs use mg/dL; most other countries use µmol/L.
Every equation side by side
| Equation | Result | Stage |
|---|
The 2009 and MDRD equations are old and shown only to compare with older lab reports, without the race factor they once used. MDRD is not reliable above 60.
Kidney risk grid (KDIGO)
| Stage | A1under 30 mg/g | A230–300 mg/g | A3over 300 mg/g |
|---|---|---|---|
| G1 | low | moderate | high |
| G2 | low | moderate | high |
| G3a | moderate | high | very high |
| G3b | high | very high | very high |
| G4 | very high | very high | very high |
| G5 | very high | very high | very high |
Add a urine ACR result to see your square. Risk means the chance of kidney disease getting worse, from KDIGO.
How your eGFR is worked out
Your numbers, step by step, with the CKD-EPI 2021 equation.
- 1
Scale your creatinine
0.9 ÷ 0.7
= 1.29 - 2
Apply the powers
1.29^−1.2
= 0.740 - 3
Age and sex
0.9938^50 × 1.012
= 0.742 - 4
Your eGFR and stage
142 × 0.740 × 0.742
= 78 → G2
Read more: the formula, a worked example, stages and notes
Your kidneys filter waste out of your blood. Measuring that filtering directly is slow, so labs estimate it, the eGFR (estimated glomerular filtration rate), from the level of creatinine in your blood. Creatinine is a waste product from muscle: when kidneys filter less, it builds up. The equation also uses your age and sex, because muscle mass and creatinine change with both. The result is in mL per minute, scaled to an average adult body size of 1.73 m².
Your lab report almost always shows your eGFR already. Use this to understand it, compare equations or check an older result. Only a doctor can diagnose kidney disease, and these equations are not for children under 18. This is not medical advice.
The formula
CKD-EPI 2021 (creatinine): eGFR = 142 × min(creatinine ÷ κ, 1)^α × max(creatinine ÷ κ, 1)^-1.2 × 0.9938^age × 1.012 if female
κ = 0.7 for women, 0.9 for men; α = -0.241 for women, -0.302 for men; creatinine in mg/dL (µmol/L ÷ 88.42)
CKD-EPI 2021 (creatinine + cystatin C): eGFR = 135 × min(Scr ÷ κ, 1)^α × max(Scr ÷ κ, 1)^-0.544 × min(cystatin C ÷ 0.8, 1)^-0.323 × max(cystatin C ÷ 0.8, 1)^-0.778 × 0.9961^age × 0.963 if female
κ = 0.7 / 0.9; α = -0.219 for women, -0.144 for men
CKD-EPI 2012 (cystatin C): eGFR = 133 × min(cystatin C ÷ 0.8, 1)^-0.499 × max(cystatin C ÷ 0.8, 1)^-1.328 × 0.996^age × 0.932 if female
Cockcroft–Gault creatinine clearance (mL/min) = (140 − age) × weight in kg ÷ (72 × creatinine mg/dL) × 0.85 if female
Body size: BSA (DuBois) = 0.007184 × kg^0.425 × cm^0.725, and eGFR for your body size = eGFR × BSA ÷ 1.73. Ideal weight (Devine) = 50 kg for men or 45.5 kg for women + 2.3 kg per inch over 5 feet; adjusted weight = ideal + 0.4 × (actual − ideal). The old equations, for comparison only: CKD-EPI 2009 = 141 × min(Scr ÷ κ, 1)^α × max(Scr ÷ κ, 1)^-1.209 × 0.993^age × 1.018 if female (α -0.329 / -0.411); MDRD = 175 × Scr^-1.154 × age^-0.203 × 0.742 if female. They once multiplied by 1.159 and 1.212 for Black patients; that race factor is left out here and is no longer recommended.
Worked example
A 50-year-old woman with a creatinine of 0.9 mg/dL (0.9 × 88.42 = 79.6 µmol/L). For women κ = 0.7, so 0.9 ÷ 0.7 = 1.2857. That's above 1, so the first term is 1 and the second is 1.2857^−1.2 = 0.7396. The age term is 0.9938^50 = 0.7327, and the female factor is 1.012. eGFR = 142 × 0.7396 × 0.7327 × 1.012 = 77.9, shown as 78 mL/min/1.73 m². That is stage G2 (mildly decreased); the typical eGFR for ages 50–59 is about 93.
If she also weighs 70 kg and is 165 cm tall, her Cockcroft–Gault creatinine clearance is (140 − 50) × 70 ÷ (72 × 0.9) × 0.85 = 6,300 ÷ 64.8 × 0.85 = 82.6 mL/min. Her BSA is 0.007184 × 70^0.425 × 165^0.725 = 1.77 m², so her eGFR for her body size is 77.9 × 1.77 ÷ 1.73 = 79.7 mL/min.
KDIGO stages (eGFR in mL/min/1.73 m²)
| Stage | eGFR | Meaning |
|---|---|---|
| G1 | 90 or more | Normal or high |
| G2 | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | under 15 | Kidney failure |
Chronic kidney disease (CKD) means an eGFR under 60, or signs of kidney damage such as albumin in the urine (ACR 30 mg/g or 3 mg/mmol and above), lasting more than 3 months. Urine ACR categories: A1 under 30 mg/g (under 3 mg/mmol), A2 30–300 mg/g (3–30 mg/mmol), A3 over 300 mg/g (over 30 mg/mmol). Stages and the risk grid follow the KDIGO CKD guideline.
Typical eGFR by age
| Age | Average eGFR |
|---|---|
| 20–29 | 116 |
| 30–39 | 107 |
| 40–49 | 99 |
| 50–59 | 93 |
| 60–69 | 85 |
| 70+ | 75 |
Averages as published by the National Kidney Foundation; eGFR slowly falls with age in healthy people too.
Notes
- The CKD-EPI 2021 equations come from Inker and others, NEJM 2021, and are the ones the National Kidney Foundation and NIDDK recommend for adults in the US. The cystatin C equation is from NEJM 2012; the old ones from 2009 and 2006 (MDRD); Cockcroft–Gault from 1976.
- Creatinine must come from a standardised (IDMS-traceable) lab test, which nearly all labs use now.
- For medicine doses, drug labels may use Cockcroft–Gault creatinine clearance or eGFR, and for very large or small people eGFR in mL/min for body size. Practice varies; your doctor or pharmacist will choose. Never change a dose yourself.
- eGFR is less reliable in pregnancy, with sudden kidney injury, very high or low muscle mass, amputation, vegetarian or high-meat diets and creatine supplements. Cystatin C helps in many of these cases.
Common questions
What is a normal eGFR?
An eGFR of 90 or more is normal or high (stage G1). 60–89 is mildly lower (G2), which is common as people get older and is not kidney disease on its own. The National Kidney Foundation gives an average of about 116 for people in their 20s, 93 in their 50s and 75 at 70 and over.
What eGFR means chronic kidney disease?
Doctors diagnose chronic kidney disease (CKD) when eGFR stays under 60 for more than 3 months, or when there are signs of kidney damage, such as albumin in the urine (an ACR of 30 mg/g or 3 mg/mmol or more), at any eGFR. Stages run from G3a (45–59) to G5 (under 15). Only a doctor can diagnose it.
Why does the 2021 equation not use race?
Older equations (CKD-EPI 2009 and MDRD) gave Black patients a higher eGFR by multiplying by a race factor. In 2021 a US task force from the National Kidney Foundation and the American Society of Nephrology recommended the new CKD-EPI 2021 equation, which uses only creatinine, age and sex, so everyone is estimated the same way.
What is cystatin C and why add it?
Cystatin C is another blood marker of kidney filtering. Unlike creatinine, it depends much less on muscle mass and diet. The CKD-EPI 2021 equation that uses both creatinine and cystatin C is the most accurate of these estimates, and KDIGO suggests it to confirm a result, for example for very muscular or very frail people.
Is eGFR the same as creatinine clearance?
No. eGFR is scaled to an average body size (mL/min per 1.73 m²) and is used to stage kidney disease. Cockcroft–Gault creatinine clearance is in mL/min for your actual body weight and is still printed on many drug labels for dose changes. Your doctor or pharmacist decides which one to use for medicines.
Can my eGFR be wrong?
Yes. Creatinine comes from muscle, so very muscular people, heavy meat meals, creatine supplements or hard exercise before the test can lower eGFR, while low muscle mass, amputation or frailty can raise it. Sudden illness and pregnancy also affect it. A single result is a snapshot; doctors look at repeat tests over 3 months.
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