Calculate eGFR using CKD-EPI 2021, MDRD, Cockcroft-Gault, and Cystatin C equations. Includes CKD staging, KDIGO risk categories, drug dosing alerts, BUN:Cr ratio, and albuminuria classification.
The Glomerular Filtration Rate (GFR) Calculator estimates kidney function using four validated equations: CKD-EPI 2021 (the recommended race-free creatinine equation), MDRD, Cockcroft-Gault, and CKD-EPI Cystatin C. GFR is the single best indicator of overall kidney function and is essential for CKD staging, drug dose adjustment, and identifying patients at risk of progressive kidney disease.
The 2021 CKD-EPI equation removed the race coefficient that was present in earlier versions, following National Kidney Foundation (NKF) and American Society of Nephrology (ASN) Task Force recommendations. This race-free equation is now the KDIGO-recommended standard for eGFR reporting worldwide. It estimates GFR from serum creatinine, age, and sex without requiring race as an input variable.
This calculator goes beyond simple GFR estimation: it provides KDIGO CKD staging (G1–G5), albuminuria categorization (A1–A3), the KDIGO risk heat map combining GFR and albuminuria, drug dosing alerts for common medications requiring renal adjustment, BUN:creatinine ratio analysis, and a comparison of all four equations with their clinical use cases. For patients where creatinine is unreliable (extreme muscle mass, vegetarian diet, liver disease), the cystatin C equation provides an alternative estimate.
Accurate GFR estimation guides virtually every aspect of CKD management: staging, prognosis, drug dosing, referral timing, and preparation for renal replacement therapy. Using the wrong equation or outdated race-based formulas can lead to diagnostic delays, missed CKD, or incorrect drug doses. This calculator compares multiple equations and flags clinical implications.
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) Glycemic Load (GL): GL = (GI × Carbs per serving) / 100
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. CKD G3b requires: nephrology referral, monitoring for anemia (CBC, ferritin), bone disease (calcium, phosphorus, PTH, vitamin D), metabolic acidosis (HCO3), and drug dose adjustments. NSAIDs should be avoided. The MDRD gives 37.4, Cockcroft-Gault gives 41.2 mL/min — cross-equation comparison helps identify potential inaccuracies.
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/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 (cisplatin), confirming CKD in borderline cases, and patients where eGFR is unreliable. Nuclear medicine GFR (⁵¹Cr-EDTA or ⁹⁹mTc-DTPA) is commonly used in the UK and Europe.
Albuminuria is not just a marker of kidney disease — it is an independent cardiovascular risk factor. Even microalbuminuria (ACR 30–300 mg/g) doubles the risk of cardiovascular events, independent of eGFR, blood pressure, and diabetes. The KDIGO risk matrix combines GFR and albuminuria categories (green = low risk, yellow = moderate, orange = high, red = very high) to guide monitoring frequency, referral, and treatment intensity. ACEi/ARB therapy reduces albuminuria and cardiovascular risk independently of blood pressure effects. SGLT2 inhibitors (dapagliflozin, empagliflozin) provide additional renoprotective and cardiovascular benefits in albuminuric CKD.
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 ≥3 months." Albuminuria (ACR ≥30 mg/g) constitutes kidney damage even with normal eGFR. A patient with eGFR 95 and ACR 200 mg/g has CKD Stage G1-A2 — this carries higher cardiovascular risk and requires ACEi/ARB therapy, blood pressure control, and regular monitoring. The KDIGO heat map shows that A2 and A3 albuminuria elevates risk even at G1 and G2 GFR stages. Always check urine albumin-to-creatinine ratio alongside eGFR for complete CKD assessment.
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.