Audited 26 Jul 2026·Last updated 28 Oct 2026·5 citations·Tier 1·0 uses

eGFR Calculator

Estimate adult kidney filtration (eGFR) from serum creatinine, age and sex with the race-free CKD-EPI 2021 equation, in mL/min/1.73 m².

eGFR Calculator

Sex (as used by CKD-EPI 2021)
Serum creatinine unit
CKD-EPI 2021 eGFR (mL/min/1.73 m2)
55.7635
Estimated glomerular filtration rate from the CKD-EPI 2021 creatinine equation, in mL/min per 1.73 m² of body surface area; it supports, and does not replace, clinical assessment.
Serum creatinine converted to mg/dL
1.1
Creatinine ratio (creatinine / kappa)
1.5714

Background.

Most people first meet eGFR as a line on a blood-test report, printed just below a creatinine result that means little on its own. A creatinine of 1.1 mg/dL can be ordinary for a muscular 30-year-old man and a sign of reduced filtration in a slight 65-year-old woman. The estimated glomerular filtration rate exists to make that distinction: it turns the creatinine value into an estimate of how many millilitres of blood the kidneys filter each minute, scaled to a standard body size.

The kidneys clear creatinine, a waste product of muscle, at a fairly steady rate, so when filtration falls the level in the blood rises. Measuring filtration directly means timed urine collections or an injected tracer, which is slow and costly. Estimating equations shortcut that by combining creatinine with age and sex, which stand in for how much creatinine a typical body makes.

The equation here is CKD-EPI 2021, published by Inker and colleagues in the New England Journal of Medicine. Its 2009 predecessor multiplied the result by a coefficient for Black patients; the 2021 version was refitted without any race term, and NIDDK lists it as the creatinine equation for adults. Enter age, sex and creatinine and you get the same figure a laboratory using this equation would report, along with the creatinine converted to mg/dL and the ratio the equation is built on.

An estimate is still an estimate. Creatinine reflects muscle as well as kidneys, so very muscular or very frail people, amputees, people taking creatine supplements and anyone whose kidney function is changing quickly can get a misleading number. Chronic kidney disease is diagnosed from results that persist over time, together with urine albumin and the clinical picture, never from one blood test. The result is a starting point for that conversation with a clinician, and it supports rather than replaces clinical judgement.

What is egfr calculator?

Glomerular filtration rate (GFR) is the volume of plasma the glomeruli, the kidneys' filtering units, clear each minute. The estimated GFR from CKD-EPI 2021 is reported in mL/min/1.73 m²: filtration per minute, rescaled as if the person had a body surface area of 1.73 square metres, a long-standing reference size for an average adult. Indexing lets results from people of different sizes be compared on one scale, which is how chronic kidney disease is staged. It also means the number is not the person's absolute filtration. That figure, in plain mL/min, is the indexed eGFR multiplied by the person's own body surface area and divided by 1.73. GFR is the standard yardstick of kidney function because filtration falls as working nephrons are lost, and because many medicines and waste products leave the body mainly by filtration. The creatinine-only equation used here is one of several. CKD-EPI 2021 also has versions that add cystatin C, a second blood marker, and those are not computed here.

How to use this calculator.

  1. Enter age in whole years. The equation was developed in adults, and ages below 18 are not accepted; children's kidney function is estimated with height-based paediatric equations instead.
  2. Choose female or male. The equation uses sex to adjust for average differences in muscle mass, and therefore in how much creatinine the body makes.
  3. Enter serum creatinine and pick the matching unit. Reports outside the United States often give it in micromol/L; type the number exactly as printed and select micromol/L, and the calculator converts it to mg/dL itself, so 97 micromol/L is read as about 1.10 mg/dL.
  4. Read the eGFR, then check the converted creatinine to confirm the unit was understood. The ratio shows which side of the equation's bend your creatinine falls on.
  5. Compare the result with the eGFR on your lab report and discuss it with your clinician alongside any urine albumin result and earlier tests. Cooked meat and strenuous exercise in the day before the blood draw can raise creatinine for a while, so a surprising result taken after either is worth repeating.

The formula.

eGFR = 142 × min(Scr⁄κ,1)^α × max(Scr⁄κ,1)^−1.200 × 0.9938^age
Scr · serum creatinine in mg/dLκ · creatinine at the curve's bend: 0.7 women, 0.9 menα · exponent below the bend: −0.241 women, −0.302 men−1.200 · exponent above the bend, both sexes0.9938^age · decline with age, age in years1.012 · final factor applied for women

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 is 0.7 for women and 0.9 for men: roughly the creatinine level at which the curve changes slope for each sex. α is −0.241 for women and −0.302 for men. The min and max terms split the creatinine effect in two. Below κ, the ratio is raised to the shallow exponent α and the max term equals 1, so very low creatinine raises the estimate only gently: for a 65-year-old woman, creatinine of 0.7, 0.6 and 0.5 mg/dL gives 95.9, 99.5 and 104.0. A strikingly high eGFR therefore often reflects low muscle mass rather than unusually strong kidneys. Above κ, the min term equals 1 and the ratio is raised to −1.200, a steep penalty: doubling creatinine above the bend multiplies eGFR by 2^−1.2, about 0.435, cutting it by more than half. The age term, 0.9938^age, lowers the estimate by about 0.62% for every year of age, or about 6% per decade; with identical creatinine, a 65-year-old is estimated about 25% lower than an 18-year-old (0.9938^47 = 0.7465). The female factor 1.012 is a small final adjustment; most of the difference between the sexes comes from κ and α. The coefficient 142 and the exponents were fitted to adults whose GFR had been measured directly with a filtration marker, and even in that kind of population a meaningful minority of individual estimates miss the measured value by more than 30%. The equation also assumes a steady state, with creatinine production and excretion in balance. When kidney function is changing fast, as in acute kidney injury, creatinine lags behind the true filtration rate and the estimate is unreliable in either direction.

A worked example.

Example

A 65-year-old woman has a serum creatinine of 1.1 mg/dL. As a woman, her constants are κ = 0.7, α = −0.241 and a sex factor of 1.012. Her creatinine ratio is 1.1 ÷ 0.7 = 1.5714. Because the ratio is above 1, the min term is 1 and the max term is 1.5714^−1.200 = 0.5814. The age term is 0.9938^65 = 0.6675. Multiplying through, 142 × 1 × 0.5814 × 0.6675 × 1.012 gives an eGFR of 55.7635, shown as 55.8 mL/min/1.73 m². The same creatinine in a 65-year-old man gives 74.5 mL/min/1.73 m². His κ of 0.9 makes the ratio 1.1 ÷ 0.9 = 1.2222, and 1.2222^−1.200 = 0.7860, so the creatinine penalty is far milder; 142 × 0.7860 × 0.6675 × 1 = 74.5. Thirty fewer years would move her estimate less than a doubled creatinine would: at 35 with the same creatinine she would get 67.2, while a creatinine of 2.2 at 65 would bring her to 24.3. What 55.8 means for her depends on whether a repeat test months later gives a similar figure and on her urine albumin result. Her clinician will read it against KDIGO's categories and her earlier results, not in isolation.

age Years65
serum Creatinine1.1

Frequently asked questions.

Why is my eGFR lower than my partner's when our creatinine is the same?
Because the equation reads the same creatinine differently by sex and age. Women make less creatinine on average, so a given level implies lower filtration: at 65 years and 1.1 mg/dL a woman's estimate is 55.8 and a man's 74.5 mL/min/1.73 m². Age also lowers the estimate by about 0.62% a year, so an older partner will score lower on identical blood results.
Does one low eGFR mean I have chronic kidney disease?
No. Chronic kidney disease is defined by reduced filtration or signs of kidney damage that persist over time, and KDIGO guidance classifies it using both eGFR and urine albumin, together with the cause. A single low result can follow dehydration, a recent illness, a new medicine or ordinary laboratory variation, so clinicians repeat the test and read the trend before drawing conclusions.
My creatinine moved from 1.0 to 1.2. Is a 12-point drop in eGFR worrying?
For a 65-year-old woman those two values give 62.5 and 50.2 mL/min/1.73 m², so a modest shift in creatinine moves the estimate a long way. Creatinine varies between tests with hydration, a large meat meal, exercise and the laboratory's method. One change of this size is a reason to repeat the test, and a clinician will look at whether it holds.
Why was the race coefficient removed?
The 2009 CKD-EPI equation gave higher estimates to patients recorded as Black, on the assumption of higher average creatinine production. Race is a social category, not a biological measurement, and the adjustment could delay diagnosis and referral. In 2021 the CKD-EPI group refitted the equation without it, and the resulting race-free equation is the one NIDDK lists for adults and the one used here. A joint task force of the National Kidney Foundation and the American Society of Nephrology recommended the switch in 2021, and many laboratories have since adopted it.
Is eGFR the same as creatinine clearance from Cockcroft-Gault?
No. Cockcroft-Gault estimates creatinine clearance in mL/min from age, weight, sex and creatinine, without indexing to body surface area. Many drug labels were written around it, so when a label specifies creatinine clearance, that is the number to use. CKD-EPI eGFR is indexed to 1.73 m² and is the measure used for staging kidney disease. The two can differ substantially in very large or small adults. The Cockcroft-Gault formula is (140 − age) × weight in kg ÷ (72 × creatinine), times 0.85 for women; for the 65-year-old woman in the example at 60 kg it gives about 48.3 mL/min against her eGFR of 55.8.
How do I convert my eGFR to plain mL/min?
Multiply it by your body surface area in square metres and divide by 1.73. For the 55.8 example, a small woman with a surface area of 1.5 m² has an absolute filtration of about 48.3 mL/min, while a larger person at 2.1 m² would have about 67.7 mL/min. The conversion matters mostly for drug dosing at the extremes of body size.
When is a creatinine-based eGFR likely to be wrong?
Whenever creatinine production is far from typical for age and sex: very high muscle mass, wasting or frailty, limb amputation, paralysis, a strict vegetarian diet or creatine supplements. Some medicines, including trimethoprim and cimetidine, block the tubular secretion of creatinine and raise blood levels without changing filtration. The equation also assumes a steady state, so it misleads while function is changing quickly. Pregnancy is outside the equation too: filtration rises substantially in a normal pregnancy and creatinine falls.
What does cystatin C add?
Cystatin C is a protein made by nearly all cells, so its blood level depends much less on muscle mass than creatinine does. CKD-EPI 2021 includes equations that use cystatin C alone or together with creatinine, and the combined version estimates GFR more accurately. The KDIGO 2024 guideline suggests using the combined equation when a creatinine-based estimate is thought to be less accurate, for instance at extremes of muscle mass. This calculator does not compute the cystatin C equations.
Which sex should transgender or nonbinary people enter?
The equation's sex terms stand in for average muscle mass, so neither choice may fit someone whose body composition has changed with hormone therapy. NIDDK's guidance on demographic factors discusses this. Clinicians sometimes calculate the estimate both ways and consider the range, or turn to cystatin C, which is less tied to muscle. A clinician who knows the person's history should make that call.
Why might my laboratory report a different eGFR from this one?
Laboratories do not all use the same equation. Some still report the 2009 CKD-EPI or the older MDRD equation, and many European laboratories have adopted the EKFC equation, each of which gives somewhat different numbers from the same creatinine. Rounding of a micromol/L result and the laboratory's creatinine method also play a part. If the gap is large, check which equation your report names.

References& sources.

  1. [1]National Institute of Diabetes and Digestive and Kidney Diseases (2024). eGFR Equations for Adults. NIDDK.
  2. [2]National Institute of Diabetes and Digestive and Kidney Diseases. Estimated Glomerular Filtration Rate (eGFR) Calculators. NIDDK.
  3. [3]Inker, L.A. et al. (2021). New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. New England Journal of Medicine.
  4. [4]Kidney Disease: Improving Global Outcomes (2024). KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. KDIGO.
  5. [5]National Institute of Diabetes and Digestive and Kidney Diseases. Factors Affecting eGFR Accuracy: Demographics. NIDDK.

How this page was produced

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Method
eGFR = 142 × min(Scr⁄κ,1)^α × max(Scr⁄κ,1)^−1.200 × 0.9938^age
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