Estimate kidney filtration using CKD-EPI 2021, MDRD, Cockcroft-Gault, and cystatin C equations. Includes CKD staging context, albuminuria categories, and equation comparison for medication-review or referral discussions.
The Glomerular Filtration Rate (GFR) Calculator estimates kidney filtration with four commonly used equations: CKD-EPI 2021, MDRD, Cockcroft-Gault, and CKD-EPI cystatin C. eGFR is widely used for CKD staging and medication review, but it remains an estimate rather than a direct measurement of filtration.
The 2021 CKD-EPI creatinine equation removed the race coefficient used in earlier versions after National Kidney Foundation (NKF) and American Society of Nephrology (ASN) Task Force recommendations. It is now the default reporting equation in many settings and a common current standard for adult creatinine-based eGFR.
This calculator can organize CKD stage, albuminuria category, and equation comparison in one place. Medication dosing, referral decisions, and CKD diagnosis should still be confirmed against current guidelines, repeat testing, and the clinical context.
Equation choice can matter near staging and dosing thresholds, and side-by-side comparison can make those differences easier to see. The calculator is best used as a structured reference and discussion aid rather than a substitute for lab reporting, repeat measurements, or clinician judgment.
CKD-EPI 2021 (Race-Free): eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age × [1.012 if female] Where: κ = 0.7 (F), 0.9 (M); α = −0.241 (F), −0.302 (M) MDRD: eGFR = 175 × Scr^−1.154 × Age^−0.203 × [0.742 if female] Cockcroft-Gault: CrCl = [(140 − Age) × Weight (kg) × (0.85 if female)] / (72 × Scr)
Result: CKD-EPI 2021: 38.9 mL/min/1.73m² — CKD Stage G3b
Using the CKD-EPI 2021 equation with Scr 1.4 mg/dL in a 62-year-old female: κ=0.7, α=−0.241, Scr/κ = 2.0 (>1), so eGFR = 142 × 1^(−0.241) × 2.0^(−1.200) × 0.9938^62 × 1.012 = ~38.9. That falls in a range often labeled CKD G3b if the abnormality is persistent, but staging should be interpreted alongside repeat testing, albuminuria, medications, and whether acute kidney injury is present. The MDRD and Cockcroft-Gault results are shown for comparison because equation choice can change the number meaningfully near decision thresholds.
The CKD-EPI 2021 equation was developed from a pooled dataset of 12 studies (N = 15,049) without using race as a variable. Compared to CKD-EPI 2009 without the race coefficient, the 2021 equation shows less bias and similar precision. For Black individuals, the 2021 equation generally produces slightly lower eGFR estimates than the 2009 equation with the race coefficient, which may lead to earlier CKD detection and referral. For non-Black individuals, results are very similar to CKD-EPI 2009. The MDRD equation, while historically important, systematically underestimates GFR above 60 mL/min and should no longer be the primary reporting equation.
The gold standard for GFR measurement is clearance of an exogenous filtration marker: iohexol, iothalamate, inulin, or ⁵¹Cr-EDTA. Measured GFR (mGFR) involves IV injection of the marker and timed blood or urine sampling. It is expensive and time-consuming, so it is reserved for situations requiring high accuracy: kidney donor evaluation, clinical trials, monitoring nephrotoxic chemotherapy, confirming CKD in borderline cases, and patients where eGFR is unreliable.
Albuminuria is an independent kidney and cardiovascular risk marker, not just a CKD staging detail. The KDIGO risk matrix combines GFR and albuminuria categories to guide monitoring intensity and referral discussions. Medication choices such as renin-angiotensin system blockers or SGLT2 inhibitors depend on the broader diagnosis, lab pattern, and clinician review rather than eGFR alone.
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This page calculates kidney-function estimates with the CKD-EPI 2021 creatinine equation, the MDRD equation, Cockcroft-Gault creatinine clearance, and an optional cystatin C equation when that value is entered. It then places the creatinine-based estimate beside CKD stage and albuminuria context so equation differences are easier to compare near staging or dosing thresholds.
These values are estimates, not measured filtration. Acute kidney injury, unstable creatinine, unusual muscle mass, amputations, pregnancy, and medication effects can all make the estimate less reliable than the displayed number suggests.
The CKD-EPI 2009 and MDRD equations included a race coefficient (multiplied eGFR by 1.159 for Black patients) based on the observation that Black individuals in the study cohort had higher average creatinine at the same measured GFR. However, this coefficient: 1) conflated race with biological characteristics (muscle mass, diet, genetics), 2) led to delayed CKD diagnosis in Black patients (higher eGFR → earlier disease missed), 3) delayed referral and transplant listing, and 4) perpetuated racial bias in clinical practice. The 2021 NKF-ASN Task Force recommended race-free equations, and the CKD-EPI 2021 re-fit the equation without race as a variable. KDIGO now endorses the race-free equation worldwide.
CKD-EPI 2021 (creatinine) is the default for all adults. Use Cockcroft-Gault only when a specific drug label requires it (many FDA-approved drug labels were based on CG). Use CKD-EPI Cystatin C when creatinine is unreliable (extremes of muscle mass, vegetarian diet, recent meat meal, creatine supplements). Use combined creatinine-cystatin C equation for maximum accuracy when both are available. For children, none of these equations apply — use the Schwartz or CKiD equations instead.
GFR measures the volume of plasma filtered by the glomeruli per minute (the "true" measure of kidney function). Creatinine clearance (CrCl) measures the volume of plasma cleared of creatinine per minute. They differ because creatinine is not only filtered but also secreted by the proximal tubule, making CrCl ~10–15% higher than GFR. This difference increases as GFR declines (proportionally more tubular secretion). CKD-EPI and MDRD estimate GFR; Cockcroft-Gault estimates CrCl. For clinical purposes, they are often used interchangeably, but for drug dosing, use whichever the drug label specifies.
Yes. eGFR equations are population-level estimations with imprecision of ±30% (a reported eGFR of 60 could be truly 42–78). Common causes of inaccuracy: 1) Extreme muscle mass (bodybuilders: creatinine high, eGFR falsely low), 2) Malnutrition/amputees (low creatinine, eGFR falsely high), 3) Acute kidney injury (creatinine is rising and hasn't equilibrated — eGFR overestimates function), 4) Vegetarian diet (lower creatinine from lower creatine intake), 5) Drugs that inhibit creatinine secretion (trimethoprim, cimetidine — raise creatinine without changing GFR), 6) Pregnancy (GFR increases physiologically; equations may not apply). When precise GFR is needed, consider measured GFR (iohexol or iothalamate clearance).
eGFR ≥60 does not rule out CKD. CKD is defined as kidney damage or GFR <60 for at least 3 months. Albuminuria (ACR ≥30 mg/g) can represent kidney damage even with normal eGFR. A patient with eGFR 95 and ACR 200 mg/g may still fall into a CKD risk category, which is why urine albumin-to-creatinine ratio matters alongside eGFR.
KDIGO guidelines recommend nephrology referral for: 1) eGFR <30 (CKD G4–G5), 2) Significant albuminuria (ACR >300 mg/g), 3) Rapid progression (eGFR decline >5 mL/min/year), 4) Persistent hematuria after urological evaluation, 5) Resistant hypertension (≥4 anti-hypertensives), 6) Persistent electrolyte abnormalities (hyperkalemia, metabolic acidosis), 7) Recurrent kidney stones, 8) Hereditary kidney disease suspected (polycystic kidney disease). Earlier referral (G3b) is recommended for complex patients. Timely referral to nephrology improves outcomes — late referral (first seen by nephrology <3 months before dialysis) is associated with increased mortality.