acalculator

What is my GFR?

Enter a creatinine or cystatin C result, your age, and your sex to estimate your glomerular filtration rate (eGFR) and its KDIGO category. For information only. This is not medical advice or a diagnosis. Do not use it to make treatment decisions without a clinician. No licensed clinician has reviewed this page.

Your numbers

Creatinine units
Sex
Estimated GFR
92

Your estimated GFR is 92 mL/min/1.73 m², KDIGO category G1: normal or high.

G1: normal or high

  1. G5: kidney failure
  2. G4: severely decreased
  3. G3b: moderately to severely decreased
  4. G3a: mildly to moderately decreased
  5. G2: mildly decreased
  6. G1: normal or high
KDIGO GFR category
G1: normal or high
Creatinine in the other unit
88 µmol/L

Estimated GFR: 92. Your estimated GFR is 92 mL/min/1.73 m², KDIGO category G1: normal or high.

Which GFR category?

This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use

How to calculate

Estimates glomerular filtration rate (eGFR) for adults from serum creatinine, cystatin C, or both, with the race-free 2021 CKD-EPI equations, and shows the KDIGO GFR category.

Example with the default inputs (Equation Creatinine (CKD-EPI 2021), Creatinine units mg/dL, Serum creatinine (mg/dL) 1, Age 50, Sex Male): Your estimated GFR is 92 mL/min/1.73 m², KDIGO category G1: normal or high.

Method: CKD-EPI 2021 creatinine: 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (women), κ 0.7 (women) or 0.9 (men), α −0.241 (women) or −0.302 (men); CKD-EPI 2021 creatinine-cystatin C and 2012 cystatin C as stated in content.mdx. Scr in mg/dL, Scys in mg/L.

  • Adults 18 and older with stable kidney function (not acute kidney injury).
  • Creatinine is IDMS-standardized and cystatin C is standardized to the IFCC reference material. µmol/L is converted with 1 mg/dL = 88.4 µmol/L.
  • The equations do not use race (Inker 2021; NKF-ASN Task Force 2021).
  • eGFR is per 1.73 m² of body surface area and is rounded to a whole number; the KDIGO category is read from the whole number.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Equation Creatinine (CKD-EPI 2021), Creatinine units mg/dL, Serum creatinine (mg/dL) 1, Age 50, Sex Male gives Estimated GFR 92, KDIGO GFR category G1: normal or high.Source: Inker et al., N Engl J Med 2021 (CKD-EPI 2021 creatinine): 142 × (1.0/0.9)^−1.200 × 0.9938^50 = 91.69, shown as 92
  2. Equation Creatinine (CKD-EPI 2021), Creatinine units µmol/L, Serum creatinine (µmol/L) 132.6, Age 70, Sex Female gives Estimated GFR 37, KDIGO GFR category G3b: moderately to severely decreased, Creatinine in the other unit 1.50 mg/dL.Source: Inker et al. 2021: 132.6 ÷ 88.4 = 1.5 mg/dL
  3. Equation Creatinine and cystatin C (CKD-EPI 2021), Creatinine units mg/dL, Serum creatinine (mg/dL) 1.2, Cystatin C (mg/L) 1.1, Age 60, Sex Male gives Estimated GFR 71, KDIGO GFR category G2: mildly decreased.Source: Inker et al. 2021 (creatinine-cystatin C): 135 × (1.2/0.9)^−0.544 × (1.1/0.8)^−0.778 × 0.9961^60 = 71.28, shown as 71
  4. Equation Cystatin C (CKD-EPI 2012), Cystatin C (mg/L) 1.4, Age 45, Sex Female gives Estimated GFR 49, KDIGO GFR category G3a: mildly to moderately decreased.Source: Inker et al., N Engl J Med 2012 (CKD-EPI cystatin C): 133 × (1.4/0.8)^−1.328 × 0.996^45 × 0.932 = 49.22, shown as 49

Medical disclaimer

This calculator is for information and education only. It is not medical advice, and its result is not a diagnosis. Do not use it to start, stop, or change a treatment without a clinician who knows your health history. No licensed clinician has reviewed this page. This site's editors checked the formulas and worked examples against published sources. If you think you have a medical emergency, call your local emergency number.

When this does not apply. The equations were built and checked in adults 18 and older (Inker 2021). Do not use them for children, in pregnancy, when creatinine is changing quickly (acute kidney injury), on dialysis, or at extremes of muscle mass, for example after an amputation.

How the GFR is estimated

Scr is serum creatinine in mg/dL. A value in µmol/L is divided by 88.4 (KDIGO 2012). Scys is serum cystatin C in mg/L. Age is in whole years. "min(x, 1)" is the smaller of x and 1, and "max(x, 1)" the larger.

2021 CKD-EPI creatinine (the default)

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 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

2021 CKD-EPI creatinine-cystatin C

eGFR = 135 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−0.544 × min(Scys/0.8, 1)^−0.323 × max(Scys/0.8, 1)^−0.778 × 0.9961^age × 0.963 (if female)

  • κ = 0.7 for women, 0.9 for men
  • α = −0.219 for women, −0.144 for men

2012 CKD-EPI cystatin C

eGFR = 133 × min(Scys/0.8, 1)^−0.499 × max(Scys/0.8, 1)^−1.328 × 0.996^age × 0.932 (if female)

Rounding and category

The eGFR is rounded to the nearest whole number (halves round up, read from the decimal value: a result within 1e-9 (relative) of a half counts as the half, so 2.005 rounds to 2.01), as labs report it. The KDIGO 2012 category is read from that whole number, lower bound included: G1 90 or more, G2 60 to 89, G3a 45 to 59, G3b 30 to 44, G4 15 to 29, G5 under 15. The "other unit" row shows the creatinine as typed, converted: mg/dL × 88.4 rounded to a whole µmol/L with a thousands separator (1,717 µmol/L), or µmol/L ÷ 88.4 to two decimals. Both round halves up from the decimal value, so 88.842 µmol/L (1.005 mg/dL) shows as 1.01 mg/dL.

Inputs the calculator accepts

  • Age 18 to 110 years. Creatinine 0.1 to 20 mg/dL (8.84 to 1,768 µmol/L). Cystatin C 0.2 to 10 mg/L.
  • None of the three equations uses race.

Limits

An eGFR is not reliable when creatinine is changing quickly (acute kidney injury), at extremes of muscle mass, in amputees, with a very high meat or creatine intake, or with drugs that change creatinine secretion (for example trimethoprim). A chronic kidney disease diagnosis needs an eGFR below 60, or signs of kidney damage, for 3 months or more.

Worked examples by hand

Man, 50, creatinine 1.0 mg/dL (creatinine equation). Scr/κ = 1.0 ÷ 0.9 = 1.1111, so the min term is 1 and the max term is 1.1111^−1.200 = 0.88123. 0.9938^50 = 0.73274. eGFR = 142 × 0.88123 × 0.73274 = 91.69, shown as 92, G1.

Woman, 70, creatinine 132.6 µmol/L (creatinine equation). 132.6 ÷ 88.4 = 1.5 mg/dL. Scr/κ = 1.5 ÷ 0.7 = 2.1429, max term = 2.1429^−1.200 = 0.40069. 0.9938^70 = 0.64704. eGFR = 142 × 0.40069 × 0.64704 × 1.012 = 37.26, shown as 37, G3b.

Man, 60, creatinine 1.2 mg/dL, cystatin C 1.1 mg/L (creatinine-cystatin C). Scr/κ = 1.3333, max term = 1.3333^−0.544 = 0.85513. Scys/0.8 = 1.375, max term = 1.375^−0.778 = 0.78055. 0.9961^60 = 0.79100. eGFR = 135 × 0.85513 × 0.78055 × 0.79100 = 71.28, shown as 71, G2.

Woman, 45, cystatin C 1.4 mg/L (cystatin C equation). Scys/0.8 = 1.75, max term = 1.75^−1.328 = 0.47560. 0.996^45 = 0.83497. eGFR = 133 × 0.47560 × 0.83497 × 0.932 = 49.22, shown as 49, G3a.

Other questions people ask

What is GFR?

Glomerular filtration rate (GFR) is the volume of blood plasma that the kidneys filter each minute. It is the best overall measure of kidney function. Measuring it directly needs a special test, so labs estimate it (eGFR) from a blood marker, age, and sex.

Which equation does this GFR calculator use?

By default, the 2021 CKD-EPI creatinine equation (Inker and others, 2021). You can also pick the 2021 creatinine-cystatin C equation or the 2012 cystatin C equation. The National Kidney Foundation and the American Society of Nephrology recommend these race-free equations for adults in the US.

What is a normal eGFR?

KDIGO calls an eGFR of 90 or more "normal or high" (G1) and 60 to 89 "mildly decreased" (G2). Below 60 for 3 months or more meets the definition of chronic kidney disease. eGFR falls slowly with age, so a value in the 60s can be common in older adults.

Why does the result say mL/min/1.73 m²?

The equations give GFR scaled to a standard body surface area of 1.73 m², so results can be compared between people of different sizes. Drug labels sometimes use creatinine clearance in mL/min instead; see the creatinine clearance calculator for Cockcroft-Gault.

When is cystatin C used?

Creatinine depends on muscle mass and diet. Cystatin C does not, so KDIGO suggests adding it when a creatinine-based eGFR may be wrong, for example with very high or low muscle mass, or to confirm chronic kidney disease. The combined creatinine-cystatin C equation is the most accurate of the three.

Can I use this for children or during pregnancy?

No. These equations were built and tested in adults 18 and older who were not pregnant. Children need a pediatric equation, and pregnancy changes kidney filtration.