eGFR calculator using the CKD-EPI 2021 equations
For healthcare professionals and students. Check results against your local protocols and clinical judgement; this tool does not give medical advice.
This eGFR calculator estimates glomerular filtration rate with the race-free CKD-EPI 2021 creatinine equation recommended in the US by the National Kidney Foundation and the American Society of Nephrology, and also offers the 2012 cystatin C and 2021 creatinine–cystatin C equations. Enter age, sex and serum creatinine in mg/dL or µmol/L (and cystatin C in mg/L if you have it), and it returns eGFR in mL/min/1.73 m² with the KDIGO GFR category from G1 to G5.
All three estimates are shown side by side when you have both markers, with the working written out, so you can see how much a cystatin C result changes the picture. It runs in your browser.
How to use the eGFR Calculator
- Choose the equation: creatinine, cystatin C, or both combined.
- Enter the age (18 or over) and choose the sex.
- Enter the serum creatinine and pick mg/dL or µmol/L, and/or the cystatin C in mg/L.
- Read the eGFR, the G category and where it sits on the bar.
- Check the warnings, then copy the summary if needed.
eGFR Calculator features
Race-free 2021 equation
CKD-EPI 2021 creatinine, without the race coefficient of the 2009 version.
Cystatin C options
2012 cystatin C and 2021 creatinine–cystatin C, which the NKF recommends using more widely, especially to confirm a borderline creatinine-based result.
mg/dL or µmol/L
Creatinine in either unit, converted with 1 mg/dL = 88.4 µmol/L.
KDIGO G category
G1 to G5 from the 2024 KDIGO guideline, with the caveat that G1–G2 need markers of damage to count as CKD.
Checks
Rejects children, flags unit mix-ups and extreme values, and reminds you of the steady-state assumption.
CKD-EPI 2021 equations
From Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C–based equations to estimate GFR without race. N Engl J Med 2021;385:1737–1749 and, for cystatin C alone, Inker LA et al. N Engl J Med 2012;367:20–29. Constants as published on the National Kidney Foundation’s equation pages (checked 19 October 2026). Creatinine (Scr) in mg/dL, standardised to IDMS; cystatin C (Scys) in mg/L, standardised to IFCC reference material.
| Equation | Formula | κ and α |
|---|---|---|
| Creatinine 2021 | 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 [female] | κ 0.7 F / 0.9 M; α −0.241 F / −0.302 M |
| Cystatin C 2012 | 133 × min(Scys/0.8, 1)^−0.499 × max(Scys/0.8, 1)^−1.328 × 0.996^age × 0.932 [female] | — |
| Creatinine–cystatin C 2021 | 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 [female] | κ 0.7 F / 0.9 M; α −0.219 F / −0.144 M |
Worked example and GFR categories
A 50-year-old man with creatinine 1.0 mg/dL (88.4 µmol/L): Scr/κ = 1.111, so the max term is 1.111^−1.200 = 0.8812 and 0.9938^50 = 0.7327; eGFR = 142 × 0.8812 × 0.7327 = 91.7, reported as 92 mL/min/1.73 m². A woman of the same age and creatinine has Scr/κ = 1.429, giving 69. These are hand-calculated from the published constants, and the self-test checks them.
The GFR categories below are from the KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD (Kidney Int 2024;105(4S):S117–S314). CKD is defined by abnormal kidney structure or function present for more than 3 months; a G1 or G2 eGFR on its own is not CKD, and full staging also uses the albuminuria category (A1–A3).
| Category | eGFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | ≥ 90 | 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 | < 15 | Kidney failure |
eGFR, creatinine clearance and drug doses
eGFR is indexed to a body surface area of 1.73 m². For drug dosing some references want an un-indexed value: multiply eGFR by the patient’s body surface area ÷ 1.73 (the body surface area calculator gives it), or use the Cockcroft-Gault creatinine clearance if the drug label was written for it. Use the estimate the dosing reference specifies.
eGFR Calculator FAQ
How is eGFR calculated from creatinine?
With the CKD-EPI 2021 equation: 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.2 × 0.9938^age, × 1.012 for women, where κ and α depend on sex. The eGFR calculator above shows the working with your numbers.
Can I enter creatinine in µmol/L?
Yes. Choose µmol/L and the tool divides by 88.4 to get mg/dL before applying the equation. For example 106 µmol/L is 1.20 mg/dL.
Why was race removed from eGFR?
The 2009 CKD-EPI equation multiplied eGFR by 1.159 for Black patients. The 2021 refit dropped race; the NKF–ASN task force recommended adopting it in the US in 2021.
When should cystatin C be used?
Cystatin C is less affected by muscle mass than creatinine. Combining both markers gives the most accurate estimate and is commonly used to confirm a creatinine-based eGFR of 45–59 or when muscle mass is unusual.
What eGFR is normal?
An eGFR of 90 or more is category G1 (normal or high); 60–89 is G2. Neither is chronic kidney disease unless there are markers of kidney damage, such as albumin in the urine, for more than 3 months.
Can I use this for children?
No. CKD-EPI equations are for adults aged 18 and over; children need paediatric equations.