Health & Fitness

GFR Calculator | CKD-EPI, MDRD & Cockcroft-Gault Creatinine Clearance

Estimate Glomerular Filtration Rate (GFR) using three validated equations: CKD-EPI 2021, MDRD 4-variable, and Cockcroft-Gault. Classifies CKD stage (G1–G5) per KDIGO 2022 guidelines, shows creatinine clearance, and flags dose-adjustment thresholds.

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Serum Creatinine

Age (years)

Sex

Race (MDRD only)

Weight (kg) — for Cockcroft-Gault

What Is the GFR Calculator | CKD-EPI, MDRD & Cockcroft-Gault Creatinine Clearance?

Glomerular Filtration Rate (GFR) is the best overall index of kidney function. It measures how much blood the kidneys filter per minute. Three validated equations estimate GFR from serum creatinine: CKD-EPI 2021 is the current recommended equation (race-free, most accurate), MDRD 4-variable is an older equation that underestimates GFR above 60 mL/min, and Cockcroft-Gault estimates creatinine clearance (CrCl) which tends to be higher than true GFR. CKD staging per KDIGO 2022 uses eGFR to classify kidney function from G1 (normal) to G5 (kidney failure).

Formula

CKD-EPI 2021: eGFR = 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × [1.012 if female] · MDRD: 175 × Scr^−1.154 × age^−0.203 · CG (CrCl): ((140−age)×weight)/(72×Scr) × [0.85 if female]

How to Use

1
Enter serum creatinine from your lab report. Select mg/dL or μmol/L — the calculator converts automatically.
2
Enter the patient age in years (valid range: 18–120 years; pediatric GFR uses different equations).
3
Select sex (male or female) — both CKD-EPI and Cockcroft-Gault use sex-based multipliers.
4
Select race (Black or Other) — this is used only for the MDRD equation; CKD-EPI 2021 is race-free.
5
Enter body weight in kg — this is used only for the Cockcroft-Gault creatinine clearance estimate.
6
Click Calculate GFR to see CKD-EPI, MDRD, and Cockcroft-Gault results side by side.
7
Review the CKD stage card (G1–G5) and drug dosing flags for thresholds at eGFR < 60, < 30, and < 15.

Enter serum creatinine (in mg/dL or μmol/L using the unit toggle), age in years, sex, and body weight in kg. Select race for MDRD correction if needed. Click Calculate GFR to see all three equations, the CKD stage, and drug dosing flags.

Example Calculation

65-year-old male, serum creatinine = 1.5 mg/dL, weight = 75 kg, non-Black. CKD-EPI 2021: κ=0.9, α=−0.302, Scr/κ=1.67 > 1, eGFR = 142 × 1^−0.302 × 1.67^−1.200 × 0.9938^65 ≈ 46 mL/min/1.73m². MDRD: 175 × 1.5^−1.154 × 65^−0.203 ≈ 46. Cockcroft-Gault CrCl: (140−65)×75/(72×1.5) = 5625/108 ≈ 52 mL/min. CKD Stage G3a (mild-moderate decrease).

Understanding GFR | CKD-EPI, MDRD & Cockcroft-Gault Creatinine Clearance

CKD Stages and Clinical Implications (KDIGO 2022)

Stage	eGFR (mL/min/1.73m²)	Description	Key Actions
G1	≥ 90	Normal or high	Diagnose and treat cause, cardiovascular risk reduction
G2	60–89	Mildly decreased	Evaluate progression, control blood pressure and diabetes
G3a	45–59	Mild to moderate decrease	Monitor labs q6mo, adjust renally cleared drug doses
G3b	30–44	Moderate to severe decrease	Nephrology referral, evaluate for anemia, bone disease
G4	15–29	Severely decreased	Prepare for renal replacement therapy (dialysis/transplant)
G5	< 15	Kidney failure	Dialysis or kidney transplant; strict drug avoidance list

Drug Dosing Thresholds by eGFR

eGFR Threshold	Commonly Affected Drugs	Recommendation
< 60 mL/min	Metformin, NSAIDs, some statins, ACE inhibitors	Monitor; consider dose reduction or alternative
< 45 mL/min	Metformin (contraindicated), gadolinium contrast	Withhold or substitute; nephrology guidance
< 30 mL/min	Digoxin, direct oral anticoagulants, allopurinol	Significant dose reduction or avoidance required
< 15 mL/min	Most renally cleared drugs, potassium-sparing diuretics	Dialysis consideration; specialist management

Key Differences Between the Three Equations

›CKD-EPI 2021: Most accurate; race-free; recommended by KDIGO 2022 for all adults; best for GFR above and below 60 mL/min.
›MDRD 4-variable: Older equation; accurate for GFR < 60 but underestimates at higher GFR; still widely reported by labs; includes optional race factor.
›Cockcroft-Gault: Not GFR — estimates creatinine clearance; used for drug dosing in pharmacokinetic studies; requires body weight; higher than eGFR.
›Cystatin C: Not calculated here. Less affected by muscle mass; useful when creatinine is unreliable (sarcopenia, amputees, extreme muscle mass).

Frequently Asked Questions

What is the difference between eGFR and creatinine clearance (CrCl)?

eGFR (estimated GFR) from CKD-EPI or MDRD is normalized to 1.73 m² body surface area and better reflects true kidney filtration. Creatinine clearance from Cockcroft-Gault estimates actual mL/min without BSA normalization and is typically 10–20% higher than eGFR. CrCl is commonly used for drug dosing calculations, while eGFR is used for CKD staging.

Why does CKD-EPI 2021 not include race?

The 2021 CKD-EPI revision eliminated the race coefficient present in the 2009 equation. Research showed the Black race multiplier (1.159) led to systematic overestimation of GFR in Black patients, delaying diagnosis and treatment. The 2021 race-free equation has similar accuracy across groups and is now the standard recommended by KDIGO and most medical societies.

Which equation should I use for drug dosing?

Most pharmacokinetic studies use Cockcroft-Gault CrCl for dose adjustment, so drug labeling typically references CrCl thresholds (e.g., reduce dose if CrCl < 30 mL/min). For monitoring and staging kidney disease, use CKD-EPI 2021. When using CG for dosing, use actual body weight unless the patient is obese (then use ideal or adjusted body weight).

What are the KDIGO CKD stages?

KDIGO 2022 classifies CKD by GFR category: G1 ≥90 (normal/high), G2 60–89 (mildly decreased), G3a 45–59 (mild-moderate), G3b 30–44 (moderate-severe), G4 15–29 (severely decreased), G5 <15 (kidney failure). Full CKD diagnosis also requires albuminuria staging (A1–A3). GFR alone is used here for simplicity.

Is GFR accurate in acute kidney injury (AKI)?

No. All creatinine-based GFR estimates assume a steady-state serum creatinine. In AKI, creatinine is rising or falling rapidly and does not reflect the current filtration rate. A rising creatinine of 1.5 mg/dL in AKI may correspond to GFR much lower than a stable 1.5 mg/dL in CKD. Use clinical context and urine output when evaluating AKI.

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