eGFR Calculator (CKD-EPI 2021)

Estimated GFR by CKD-EPI 2021 (creatinine, optionally cystatin C), Cockcroft–Gault creatinine clearance and KDIGO CKD stage — with µmol/L and mg/dL conversion.

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Result

eGFR by creatinine (CKD-EPI 2021): 99 mL/min/1.73 m²
KDIGO stage: G1 — normal or high GFR (≥ 90)
eGFR by creatinine + cystatin C: enter cystatin C to calculate
Creatinine clearance (Cockcroft–Gault): 107 mL/min
Serum creatinine: 0.96 mg/dL

Calculated per Inker 2021 (CKD-EPI 2021) and Cockcroft–Gault 1976; stages per KDIGO 2012. Reference ranges are population benchmarks from the cited sources. Laboratories use their own ranges, and interpretation depends on clinical context: discuss the result with your physician.

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How it is calculated

Glomerular filtration rate is the key measure of kidney function. The CKD-EPI 2021 equation (Inker et al., NEJM) derives it from serum creatinine, age and sex without the race coefficient, which has been removed from practice. When cystatin C is available the combined CKD-EPI 2021 cr-cys equation is used — more accurate in people with atypical muscle mass (athletes, sarcopenia, amputation, vegans). The calculator also shows Cockcroft–Gault creatinine clearance, still used for drug dosing, and the KDIGO CKD stage G1–G5.

Formula

eGFRcr = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age × 1.012 [female] κ = 0.7 (female) / 0.9 (male); α = −0.241 (female) / −0.302 (male); Scr — creatinine, mg/dL (= µmol/L / 88.4) eGFRcr-cys = 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] Cockcroft–Gault (mL/min) = (140 − Age) × Weight (kg) × 0.85 [female] / (72 × Scr, mg/dL)

Limits of the method

Estimated GFR is validated for stable adults aged 18+: in acute kidney injury, pregnancy, extreme body weight or muscle mass, amputation and with drugs that affect creatinine secretion (trimethoprim, cimetidine) it is inaccurate. A single eGFR < 60 does not mean CKD — the diagnosis requires confirmation after 3 months and albuminuria assessment. Cockcroft–Gault is not indexed to body surface area and overestimates clearance in obesity.

Sources of the method

This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.

How to calculate eGFR from a blood test

Find creatinine on your report

Serum creatinine is part of basic chemistry. Labs in Europe and the CIS report µmol/L; the USA and Latin America report mg/dL. Pick the matching unit.

Set sex and age

Muscle mass — and therefore "normal" creatinine — differs between men and women and declines with age; the equation accounts for this. The race coefficient was removed in the 2021 version.

Add cystatin C if available

Cystatin C does not depend on muscle mass or diet. The combined equation is recommended by KDIGO 2024 to confirm CKD at eGFRcr 45–59 without albuminuria.

eGFR worked examples

Normal94 mL/min/1.73 m²

Woman, 32, creatinine 75 µmol/L, 62 kg

Stage G1. Cockcroft–Gault clearance 93 mL/min. Kidney function preserved.

Routine check-up monitoring; with diabetes or hypertension — yearly with albuminuria.

Mild decrease67 mL/min/1.73 m²

Man, 58, creatinine 110 µmol/L, 90 kg

Stage G2. Creatinine is formally "within reference" but GFR is reduced. Cockcroft–Gault gives 82 mL/min because of body weight — a typical discrepancy in overweight.

Without albuminuria G2 is not CKD; blood pressure and glucose control matter.

CKD G3b34 mL/min/1.73 m²

Man, 71, creatinine 180 µmol/L, 74 kg

Stage G3b, clearance 35 mL/min. Doses of renally cleared drugs need adjustment, protein limited to 0.8 g/kg, nephrology follow-up.

At G3b–G4 the dietitian calculates protein per ideal, not actual, body weight.

Why "normal creatinine" can hide reduced kidney function

Creatinine is a breakdown product of muscle creatine, so its level depends on muscle mass. In an elderly 55-kg woman, creatinine 95 µmol/L sits within the lab reference but corresponds to a GFR of about 55 — stage G3a. In a 100-kg athlete the same creatinine is normal. That is why nephrologists look at estimated GFR adjusted for sex and age rather than creatinine, and add cystatin C in doubtful cases.

GFR and nutrition: what changes at each stage

At G1–G2 there are no special restrictions — blood pressure, glucose control and avoiding excess salt matter. From G3a KDIGO recommends protein 0.8 g/kg ideal weight, sodium under 2 g/day and caution with potassium and phosphorus when elevated; NSAIDs and high-dose vitamin C become undesirable. At G4–G5 the diet is built by a nephrologist with a dietitian, and "cleansing" herbal blends and protein supplements are dangerous. High-protein weight-loss diets are not recommended in CKD.

CKD stages by GFR (KDIGO)

Stage	GFR, mL/min/1.73 m²	Meaning
G1	≥ 90	Normal; CKD only with damage markers (albuminuria, ultrasound changes)
G2	60–89	Mild decrease; often an age-related norm after 60
G3a	45–59	Moderate decrease: confirm after 3 months, albuminuria, risk-factor management
G3b	30–44	Substantial decrease: drug dose adjustment, anemia and mineral metabolism monitoring
G4	15–29	Severe decrease: nephrology care, preparation for renal replacement therapy
G5	< 15	Kidney failure: dialysis or transplantation

The full KDIGO classification also includes albuminuria (A1–A3): it is the combination of G and A that determines prognosis and monitoring frequency.

Frequently asked questions

What is a normal GFR?

In healthy adults GFR is ≥ 90 mL/min/1.73 m². After 40 it declines physiologically by about 1 mL/min per year, so 60–89 in an older person without albuminuria is a normal variant, not a disease.

How does CKD-EPI 2021 differ from CKD-EPI 2009 and MDRD?

The 2021 equation removed the race coefficient and was refit on a pooled sample. It gives values on average 3–4% higher for people to whom the coefficient was previously not applied and 3–4% lower for those to whom it was. MDRD is outdated and underestimates GFR above 60.

Why does Cockcroft–Gault clearance differ from eGFR?

The 1976 formula uses actual body weight and is not indexed to 1.73 m², so it overestimates clearance in obesity and underestimates it at low weight. It persists in drug labels because doses were historically validated against it.

Do creatine, meat and workouts affect the result?

Yes. Creatine supplementation, a large meat meal the day before and intense resistance training raise creatinine by 10–20% and lower estimated GFR. For an accurate estimate test under your usual diet without training for 24 hours, or add cystatin C.

What should I do if GFR is below 60?

Repeat the test after 3 months, get a urine albumin-to-creatinine ratio and discuss the result with a physician. CKD is diagnosed only with a persistent decrease or damage markers; a single value during dehydration or after exertion is not a diagnosis.

Should I limit protein at GFR 60–89?

No: at G1–G2 protein restriction is not recommended. Moderate restriction to 0.8 g/kg is considered from G3a, and low-protein diets (0.55–0.6 g/kg) from G4–G5 under nephrology and dietitian supervision to avoid sarcopenia.

With reduced GFR, recalculate your protein target and related markers:

Albumin-Corrected Calcium Calculator →Protein Intake Calculator (ISSN & ESPEN) →Ideal Body Weight Calculator (IBW & AdjBW) →Lab Unit Converter →

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What next

Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.

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