eGFR Calculator (CKD-EPI 2021)
Estimate glomerular filtration rate (eGFR) using the 2021 race-free CKD-EPI creatinine equation. For screening only — confirm with your doctor.
How to use this tool
- Enter serum creatinine, age and sex in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your egfr and the full breakdown beneath it.
Educational estimate — not medical advice. Consult a clinician.
This calculator uses the 2021 CKD-EPI creatinine equation (race-free version) to estimate glomerular filtration rate. eGFR is the standard measure of kidney function used to stage chronic kidney disease (CKD). A single value alone is not diagnostic; trends over time and clinical context matter.
⚠ This tool is for general information and education only and is not medical advice. Consult a qualified healthcare professional before making health decisions.
Formula
eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)−1.200 × 0.9938Age × Sf
Where: κ = 0.9 (male) or 0.7 (female); α = −0.302 (male) or −0.241 (female); Sf = 1.012 (female) or 1.0 (male).
How it works
This calculator implements the 2021 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine equation, which estimates the glomerular filtration rate — the volume of blood the kidneys filter per minute per 1.73 m2 of body surface area. The 2021 revision removed the race coefficient used in earlier versions, producing a single race-free equation validated across diverse populations. Results reflect an estimate only; a formal diagnosis of CKD requires at least two measurements taken more than 90 days apart, interpreted by a clinician alongside urinalysis and clinical history.
Worked example
- Inputs: serum creatinine (Scr) = 0.8 mg/dL, age = 40 years, sex = male.
- Set κ = 0.9, α = −0.302, sex factor = 1.0. Compute ratio = 0.8 / 0.9 = 0.889.
- Because ratio < 1: min term = 0.889−0.302 ≈ 1.035; max term = 1.0−1.200 = 1.0.
- Apply age factor: 0.993840 ≈ 0.7836.
- eGFR = 142 × 1.035 × 1.0 × 0.7836 × 1.0 ≈ 114.74 mL/min/1.73m2.
eGFR = 114.74 mL/min/1.73m² — CKD Stage G1 (normal or high).
Common mistakes to avoid
- Entering creatinine in umol/L instead of mg/dL — the 2021 CKD-EPI equation uses mg/dL, so a umol/L value must be divided by 88.4 first.
- Using a single eGFR result to diagnose CKD; the definition requires two values below threshold at least 90 days apart.
- Ignoring that acute illness or dehydration transiently raises creatinine, making eGFR appear lower than the true chronic baseline.
Key terms
- eGFR
- Estimated Glomerular Filtration Rate — the calculated volume of blood filtered by the kidneys per minute, normalised to a body surface area of 1.73 m².
- CKD-EPI
- Chronic Kidney Disease Epidemiology Collaboration — the research group that developed and validated a series of GFR-estimating equations using serum creatinine and/or cystatin C.
- Serum creatinine
- A waste product of muscle metabolism excreted by the kidneys; elevated levels indicate reduced kidney filtration capacity.
- CKD Stage
- A classification system (G1–G5) based on eGFR ranges that describes the severity of chronic kidney disease, from normal/high function (G1) to kidney failure (G5).
- Race-free equation
- The 2021 CKD-EPI revision that removed a race multiplier, applying a single set of coefficients to all patients regardless of self-reported race.
Frequently asked questions
- What is eGFR?
- Estimated glomerular filtration rate (eGFR) measures how well your kidneys filter waste from blood, expressed as mL/min/1.73 m². Normal is ≥90 for most adults.
- What changed in CKD-EPI 2021?
- The 2021 update removed the race coefficient that was present in the 2009 equation, following evidence that race is a social construct rather than a biological variable for this purpose.
- When should I see a nephrologist?
- Referral thresholds vary, but eGFR <30 (G4) generally warrants specialist review. Always discuss your results with your GP or physician.