eGFR (CKD-EPI 2021) Calculator

eGFR (CKD-EPI 2021) Calculator for Nephrology. Results map to KDIGO GFR categories: G1 >=90, G2 60-89, G3a 45-59, G3b 30-44, G4 15-29, G5 <15 mL/min/1.73 m2. CKD requires the abnormality to persist >=3 months; a single reduced value is not diagnostic. G1-G2 are only CKD if a marker of kidney damage (e.g. albuminuria) is present. G3b and below, or any category with heavy albuminuria (A3, ACR >=30 mg/mmol), signals high-to-very-high risk and typically warrants nephrology referral, while eGFR <15 indicates kidney failure and triggers planning for kidney replacement therapy. Drug dosing thresholds (commonly 60, 45, 30, 15) should ideally use non-indexed GFR for narrow-therapeutic-index or weight-extreme patients.

How this calculator works

The 2021 CKD-EPI creatinine equation estimates glomerular filtration rate from serum creatinine, age, and sex, and — unlike its 2009 predecessor — contains no coefficient for race. It is a re-fitted single log-linear spline model with sex-specific breakpoints in creatinine (0.7 mg/dL for females, 0.9 mg/dL for males) and a fixed 0.9938^age decay term; a female multiplier of 1.012 replaces the former Black-race adjustment. Output is reported in mL/min/1.73 m2 (body-surface-area indexed). A companion creatinine-cystatin C equation (eGFRcr-cys) exists and is more accurate, but this tool implements the creatinine-only version used in routine lab reporting.

When to use this calculator

Use for adults (18+) with stable kidney function to stage CKD, adjust renally cleared drugs, and screen for referral. It assumes steady-state creatinine, so it is invalid in acute kidney injury, rapidly changing function, or on dialysis. It performs poorly at extremes of muscle mass — amputees, bodybuilders, cachexia, cirrhosis, paraplegia, high-protein or creatine-supplemented diets — where cystatin C-based estimation or measured GFR is preferred. Do not apply to children (use the CKiD U25 or bedside Schwartz equations) or in pregnancy.

Inputs used

  • Serum creatinine
  • Age
  • Sex

Clinical interpretation

Results map to KDIGO GFR categories: G1 >=90, G2 60-89, G3a 45-59, G3b 30-44, G4 15-29, G5 <15 mL/min/1.73 m2. CKD requires the abnormality to persist >=3 months; a single reduced value is not diagnostic. G1-G2 are only CKD if a marker of kidney damage (e.g. albuminuria) is present. G3b and below, or any category with heavy albuminuria (A3, ACR >=30 mg/mmol), signals high-to-very-high risk and typically warrants nephrology referral, while eGFR <15 indicates kidney failure and triggers planning for kidney replacement therapy. Drug dosing thresholds (commonly 60, 45, 30, 15) should ideally use non-indexed GFR for narrow-therapeutic-index or weight-extreme patients.

Worked example

A 62-year-old woman with serum creatinine 1.3 mg/dL: creatinine exceeds the female breakpoint of 0.7, so the equation applies the steeper (1.3/0.7)^-1.200 slope times 0.9938^62 times 142 times the 1.012 female factor, yielding roughly 44 mL/min/1.73 m2. This falls in the G3b band (30-44), consistent with moderately-to-severely decreased GFR, prompting confirmation of chronicity, a urine albumin-to-creatinine ratio for full risk staging, and review of renally dosed medications.

Limitations and safety notes

The equation is precise only within about +/-30% of measured GFR in 90% of people (P30), so a reported value near a staging or dosing cutoff should not be over-interpreted. Accuracy degrades sharply when creatinine generation deviates from the age-sex norms built into the model — sarcopenia and cirrhosis overestimate GFR, high muscle mass underestimates it. Non-steady-state creatinine (evolving AKI, recent dialysis, large fluid shifts) makes any single-timepoint estimate meaningless. Because it drops race, mean estimates shifted modestly versus the 2009 equation, reclassifying some patients across CKD boundaries.

Frequently asked questions

Why did the 2021 equation remove race?

The 2009 equation raised eGFR for anyone labeled Black, a biologically unjustified adjustment that could delay CKD diagnosis, referral, and transplant listing. The 2021 refit removes race entirely while preserving overall accuracy, and is now the U.S. and KDIGO-endorsed standard.

Is the creatinine-only or the creatinine-cystatin C version better?

The combined eGFRcr-cys equation is more accurate and less biased than either single-marker version and is preferred by KDIGO when a decision hinges on a precise value or when muscle mass is atypical. This tool computes the creatinine-only estimate that most labs report by default.

My patient's eGFR is 58 — do they have CKD?

Not necessarily. G3a (45-59) meets the GFR criterion for CKD, but the value must persist for at least 3 months and reflect true kidney disease rather than transient causes. Confirm with a repeat test and check albuminuria before diagnosing.

Can I use eGFR to dose drugs like DOACs or vancomycin?

eGFR is widely used, but it is BSA-indexed (mL/min/1.73 m2) whereas many drug labels were validated against Cockcroft-Gault creatinine clearance (mL/min). For narrow-therapeutic-index drugs or patients at weight extremes, de-index to absolute mL/min or use the labeled method.

References

  • 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(19):1737-1749. PMID: 34554658.
  • Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. 2024.

Editorial review and citation methodology

Reviewed by the Quick Medical Calculator Editorial Team. Last reviewed: March 3, 2026. The review checks calculator inputs, intended population, interpretation, limitations, and source alignment.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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