Estimated glomerular filtration rate (eGFR) is the standard measure of kidney function used to stage chronic kidney disease and adjust drug doses. This tool computes eGFR with two validated creatinine-based equations and labels the result with its KDIGO stage.
Why two equations?
The CKD-EPI 2021 equation is the current standard recommended by KDIGO (Kidney Disease: Improving Global Outcomes) and most national nephrology societies. It replaced the older MDRD equation because CKD-EPI is significantly more accurate when eGFR is above 60 mL/min/1.73m² — the range where MDRD systematically underestimates kidney function and can trigger unnecessary referrals or inappropriate drug dose reductions. The 2021 refit removed the race coefficient after evidence that race is a social, not biological, variable.
The MDRD equation is retained here for two reasons: comparing it against CKD-EPI flags cases where the two methods diverge significantly (which can itself be clinically informative), and many historical records and research studies used MDRD, so cross-checking is occasionally necessary.
How it works
The race-free CKD-EPI 2021 equation, with creatinine in mg/dL, is:
eGFR = 142 × min(Scr/K, 1)^a × max(Scr/K, 1)^-1.200 × 0.9938^age
× 1.012 (if female)
female: K = 0.7, a = -0.241
male: K = 0.9, a = -0.302The legacy IDMS-traceable MDRD (175) equation is shown for comparison:
eGFR = 175 × Scr^-1.154 × age^-0.203 × 0.742 (if female)If creatinine is entered in µmol/L it is converted to mg/dL by dividing by 88.42. The CKD-EPI result is then mapped to a KDIGO G-stage.
The KDIGO G-stages
| Stage | eGFR (mL/min/1.73m²) | Description |
|---|---|---|
| G1 | ≥ 90 | Normal or high (with other evidence of CKD) |
| 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 |
Stage alone does not determine management — the KDIGO risk grid also considers albumin-to-creatinine ratio (albuminuria), and the clinical picture guides referral and treatment decisions.
Worked example
A 60-year-old man with a serum creatinine of 1.0 mg/dL:
- CKD-EPI 2021 eGFR ≈ 89 mL/min/1.73m² → Stage G2
- MDRD eGFR ≈ 75 mL/min/1.73m² → also Stage G2, but a lower numerical estimate
The gap between equations narrows at lower eGFR values (below ~60) and widens at higher values, which is exactly where CKD-EPI’s improved accuracy matters most for avoiding false diagnosis.
When eGFR is unreliable
eGFR from creatinine assumes stable kidney function and average muscle mass. It is unreliable in: acute kidney injury (creatinine is changing), pregnancy, amputees, bodybuilders, cachexia, liver cirrhosis, and when creatinine is being spuriously elevated or lowered by diet or drugs. In these situations a measured GFR or cystatin-C-based estimate may be more appropriate.
This tool provides an educational estimate. All calculations run locally in your browser and no data is transmitted anywhere.