This calculator estimates GFR with the race-free 2021 CKD-EPI creatinine equation, the one the National Kidney Foundation and the American Society of Nephrology recommend for adults 18 and older. Enter serum creatinine in mg/dL or µmol/L, age and sex. A 45-year-old man with creatinine 1.0 mg/dL has an eGFR of 94.6 mL/min/1.73 m². An eGFR below 60 for 3 months or more may be a sign of chronic kidney disease.
Sources: NIDDK, eGFR Equations for Adults; NKF, CKD-EPI creatinine equation 2021; NKF, Stages of CKD.
Body size context tools such as the BMI calculator answer different questions. Energy tools like the TDEE calculator are unrelated to filtration estimates.
How the formula works
For males, κ = 0.9 and α = -0.302. Compute Scr/κ. Then eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(-1.2) × 0.9938^age. Females use κ = 0.7, α = -0.241, and multiply by 1.012.
Worked example
Scr = 1, age = 45, male. Scr/κ = 1/0.9 ≈ 1.111. min = 1, max ≈ 1.111. eGFR = 142 × 1^(-0.302) × (1.111)^(-1.2) × 0.9938^45 ≈ 94.6.
| Input | Value |
|---|---|
| Creatinine (mg/dL) | 1 |
| Age | 45 |
| Sex | male |
| κ / α | 0.9 / -0.302 |
| Estimated eGFR | about 94.6 |
- µmol/L lab result: choose µmol/L and enter the number as reported; the calculator divides by 88.4 (88.4 µmol/L = 1 mg/dL). 106 µmol/L ÷ 88.4 = 1.20 mg/dL, an eGFR of 76.1 for a 45-year-old man. Source: NIDDK conversion factors.
- Same creatinine (1.0), same man, age 65 instead of 45: 83.5 instead of 94.6, because of the 0.9938^age term.
- Same inputs, female, age 45: 70.8 (female κ is 0.7, so creatinine 1.0 sits further above it).
- Age 50, creatinine 1.0 mg/dL. Female: 1.0 ÷ 0.7 = 1.429, so eGFR = 142 × 1.429^(-1.2) × 0.9938^50 × 1.012 = 142 × 0.652 × 0.733 × 1.012 ≈ 68.6. Male: 1.0 ÷ 0.9 = 1.111, so eGFR = 142 × 1.111^(-1.2) × 0.9938^50 = 142 × 0.881 × 0.733 ≈ 91.7.
eGFR stages (G1–G5)
| Stage | eGFR (mL/min/1.73 m²) | Meaning |
|---|---|---|
| G1 | 90 or higher | Normal filtration; CKD only if there is kidney damage (for example uACR 30 or higher) |
| G2 | 60–89 | Mildly decreased; CKD only with kidney damage |
| G3a | 45–59 | Mild to moderate loss |
| G3b | 30–44 | Moderate to severe loss |
| G4 | 15–29 | Severe loss |
| G5 | Below 15 | Kidney failure |
Stages apply when the result lasts 3 months or more. A single test does not diagnose CKD. Source: NKF, Stages of CKD.
eGFR by creatinine, age and sex
| Creatinine (mg/dL) | Male 40 | Male 60 | Male 75 | Female 40 | Female 60 | Female 75 |
|---|---|---|---|---|---|---|
| 0.7 | 119.5 | 105.5 | 96.1 | 112.1 | 98.9 | 90.1 |
| 0.9 | 110.7 | 97.8 | 89.1 | 82.9 | 73.2 | 66.7 |
| 1.0 | 97.6 | 86.2 | 78.5 | 73.0 | 64.5 | 58.8 |
| 1.2 | 78.4 | 69.2 | 63.1 | 58.7 | 51.8 | 47.2 |
| 1.5 | 60.0 | 53.0 | 48.2 | 44.9 | 39.6 | 36.1 |
| 2.0 | 42.5 | 37.5 | 34.2 | 31.8 | 28.1 | 25.6 |
| 3.0 | 26.1 | 23.1 | 21.0 | 19.5 | 17.3 | 15.7 |
How to use the fields
- Serum creatinine: enter the value from your lab report and pick its unit, mg/dL (US labs) or µmol/L (UK, Europe, Canada, Australia). µmol/L is converted by dividing by 88.4.
- Age is in years.
- Sex selects the κ, α, and female multiplier path.
Min and max limbs
When Scr/κ is at or below 1, the α exponent applies to Scr/κ and the max limb is 1. When Scr/κ is above 1, as in the default, the α limb sees 1 and the -1.2 limb sees Scr/κ. Mixing those limbs is a common hand calculation error.
Write min and max on separate lines before multiplying so the age factor is the only remaining piece.
Common mistakes
- Treating the result as a personal diagnosis
- Leaving the unit on mg/dL when the lab reports µmol/L (88 read as mg/dL instead of µmol/L gives an eGFR near zero)
- Applying male constants to a female example
- Ignoring age by omitting 0.9938^age
Educational framing only
Kidney evaluation involves labs, history, imaging, and clinical judgment. This calculator only shows how the 2021 CKD-EPI creatinine equation responds to creatinine, age, and sex.
Limitations
No cystatin C, no race coefficients from older equations, and no clinical decision support. Educational estimate only, not medical advice.
eGFR is an estimate. The 2021 creatinine equation overestimates GFR by about 4% on average in non-Black individuals and underestimates it by about 4% in Black individuals, and using creatinine with cystatin C is more accurate. Source: NIDDK, eGFR Equations for Adults.
Related: Body Surface Area Calculator, BMI Calculator, Protein Calculator, Ideal Weight Calculator.