eGFR Calculator — CKD-EPI 2021
Calculate your eGFR with the CKD-EPI 2021 formula (KDIGO race-free standard). Enter creatinine, age and sex for kidney function and CKD stage (G1–G5).
CalcVita. (2026). eGFR Calculator — CKD-EPI 2021. CalcVita. Retrieved June 4, 2026, from https://calcvita.com/en/calculators/egfr
How to use the eGFR calculator
Enter your serum creatinine (from a blood test), age, and biological sex. Select the formula — CKD-EPI 2021 is recommended by KDIGO 2024 for routine clinical use. If your doctor ordered a cystatin C test, select the combined formula for a more accurate estimate. The calculator returns your eGFR in mL/min/1.73m² and your CKD stage (G1–G5) per current guidelines.
The CKD-EPI 2021 formula explained
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^Age × [1.012 if female]. κ = 0.7 (female) / 0.9 (male). α = −0.241 (female) / −0.302 (male). This race-free version was published in 2021 (Inker LA et al., NEJM 385:1737–1749) and replaced the 2009 formula which included a race correction term that introduced systematic bias for Black patients.
CKD stages: G1 to G5
KDIGO classifies CKD into 5 eGFR-based stages: G1 (≥ 90, normal/high function), G2 (60–89, mildly decreased), G3a (45–59, mildly-moderately decreased), G3b (30–44, moderately-severely decreased), G4 (15–29, severely decreased), G5 (< 15, kidney failure). Note: CKD diagnosis requires both reduced eGFR and/or markers of kidney damage for ≥ 3 months — a single measurement is not sufficient.
Risk factors & when to seek care
Key CKD risk factors: diabetes, hypertension, family history of kidney disease, obesity, cardiovascular disease, age > 60, history of acute kidney injury. Symptoms often absent until G3b–G4, making routine lab screening essential. Seek care immediately for: sudden eGFR drop, eGFR < 30, symptoms (edema, fatigue, foamy urine, back pain), or eGFR < 60 persisting > 3 months.
Scientific References
- Inker LA, Eneanya ND, Coresh J, et al. (2021). New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race. New England Journal of Medicine 385:1737–1749. PMID 34554658
- KDIGO 2024 CKD Guideline Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International 105(4S):S117–S314.
- Inker LA, Schmid CH, Tighiouart H, et al. (2012). Estimating Glomerular Filtration Rate from Serum Creatinine and Cystatin C. New England Journal of Medicine 367:20–29. PMID 22762315
- Levey AS, Coresh J, Greene T, et al. (2006). Using Standardized Serum Creatinine Values in the Modification of Diet in Renal Disease Study Equation for Estimating GFR. Annals of Internal Medicine 145:247–254. PMID 16908915
- What is eGFR and why does it matter?
- eGFR (estimated Glomerular Filtration Rate) measures how well your kidneys filter waste from your blood, expressed in mL/min/1.73m². It is the primary metric for detecting and staging Chronic Kidney Disease (CKD). A healthy eGFR is ≥ 60, with values above 90 considered normal. Values below 60 for more than 3 months indicate CKD. Regular monitoring helps detect kidney decline early, when lifestyle interventions are most effective.
- What is the CKD-EPI 2021 formula?
- CKD-EPI 2021 is the current gold-standard formula for estimating GFR, endorsed by KDIGO (Kidney Disease: Improving Global Outcomes) in their 2024 guidelines. Unlike older formulas, CKD-EPI 2021 is race-free, removing race-based correction coefficients that introduced systematic bias. It uses serum creatinine, age, and sex. The formula is: eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(-1.200) × 0.9938^Age × 1.012 [if female]. κ = 0.7 (female) / 0.9 (male); α = -0.241 (female) / -0.302 (male).
- What are the CKD stages (G1–G5)?
- CKD is classified into 5 stages: G1 (eGFR ≥ 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 requiring dialysis or transplant evaluation). Staging helps guide treatment intensity, referral decisions, and patient counseling. Stage alone doesn't determine treatment — albuminuria levels are equally important per KDIGO 2024.
- What factors can affect my serum creatinine and eGFR?
- Creatinine is a waste product from muscle metabolism, so muscle mass significantly affects baseline creatinine. Athletes and people with high muscle mass often have higher creatinine and lower calculated eGFR, even with healthy kidneys. Conversely, elderly, malnourished, or low-muscle individuals may have falsely reassuring eGFR. Other factors: recent high-protein meals (raise creatinine), medications (NSAIDs, ACE inhibitors, contrast dye, trimethoprim), dehydration, and acute illness can all affect the reading.
- What is cystatin C and when should I use that formula?
- Cystatin C is an alternative kidney biomarker that is less affected by muscle mass than creatinine. The CKD-EPI 2012 combined formula (creatinine + cystatin C) provides the most accurate eGFR estimate and is recommended by KDIGO for confirmatory testing, especially when creatinine-based eGFR is borderline (45–60) or when muscle mass extremes may be distorting results. Cystatin C requires a separate blood test and is not part of routine metabolic panels.
- Should I see a doctor if my eGFR is below 60?
- An eGFR below 60 on a single test does not diagnose CKD — it must persist for more than 3 months and ideally be confirmed with repeat testing. However, you should consult a doctor for any eGFR below 60, especially below 45 (G3b). CKD G3–G5 requires specialist evaluation for blood pressure optimization, anemia management, mineral metabolism, and preparation for renal replacement therapy if needed. Early intervention in G3a/G3b can significantly slow disease progression.
Suggested article
eGFR and Kidney Function: Understanding CKD Stages and CKD-EPI 2021
What does your eGFR number mean? Learn how the CKD-EPI 2021 formula works, the KDIGO 2024 CKD stages (G1–G5), key risk factors for kidney disease, and when to seek medical advice.
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