🫘GFR Calculator
Calculate estimated glomerular filtration rate (eGFR) using CKD-EPI 2021 (race-free), CKD-EPI 2009, MDRD, Cockcroft-Gault, and Schwartz (pediatric) formulas. Shows CKD stage, kidney function level, and clinical guidance.
Prefer to skip the form? Scroll down and Ask AI Instead. Just describe your situation and let AI handle the math for you in seconds.
eGFR (mL/min/1.73m²)
71
eGFR by Formula
✦ Ask AI Instead
GFR Calculator: Understanding Kidney Function and CKD Stages
Glomerular filtration rate (GFR) measures how well the kidneys filter waste from the blood per minute, expressed in mL/min/1.73m². The CKD-EPI 2021 equation — the current gold standard — uses serum creatinine, age, and sex to estimate GFR without a race adjustment. Normal eGFR in healthy adults is ≥90 mL/min/1.73m²; values below 60 for ≥3 months indicate chronic kidney disease (CKD).
Formula: eGFR = 142 × min(SCr/κ, 1)^α × max(SCr/κ, 1)^(−1.200) × 0.9938^Age × 1.012 (if female)
| CKD Stage | eGFR (mL/min/1.73m²) | Category |
|---|---|---|
| G1 | ≥90 | Normal or High |
| G2 | 60–89 | Mildly Decreased |
| G3a | 45–59 | Mildly to Moderately Decreased |
| G3b | 30–44 | Moderately to Severely Decreased |
| G4 | 15–29 | Severely Decreased |
| G5 | <15 | Kidney Failure |
Our GFR calculator implements five validated equations simultaneously: CKD-EPI 2021 (the current KDIGO-recommended standard for adult eGFR), CKD-EPI 2009 (with optional race adjustment), MDRD (Modification of Diet in Renal Disease, widely used in lab reporting), Cockcroft-Gault (estimates creatinine clearance for drug dosing rather than true eGFR), and the Schwartz equation for paediatric patients. Each formula produces a slightly different value due to different mathematical models; understanding when to use which is clinically important.
The CKD-EPI 2021 Equation: Why Race Was Removed
The original CKD-EPI 2009 equation included a race adjustment that multiplied eGFR by 1.159 for Black patients, based on the observation that Black individuals had higher average serum creatinine from greater muscle mass. However, this adjustment was criticised for using race as a biological proxy rather than measuring underlying physiological variables directly, and for potentially perpetuating health disparities by delaying nephrology referral and kidney transplant listing for Black patients. In 2021, the National Kidney Foundation and American Society of Nephrology task force recommended adoption of the race-free CKD-EPI 2021 equation. Most US laboratories have since transitioned to reporting CKD-EPI 2021 eGFR values.
CKD Staging and Clinical Implications
The KDIGO (Kidney Disease: Improving Global Outcomes) 2012 guidelines classify CKD into five GFR categories (G1–G5) combined with three albuminuria categories (A1–A3). GFR alone is used for staging and monitoring progression. Stage G3a (eGFR 45–59) triggers evaluation for CKD complications including anaemia, mineral and bone disorder, and cardiovascular risk. Stage G3b (30–44) warrants nephrology referral in many guidelines. Stage G4 (15–29) requires preparation for kidney replacement therapy (dialysis or transplant). Stage G5 (<15) constitutes kidney failure.
It is critical to understand that a single eGFR measurement is insufficient to diagnose CKD — the KDIGO definition requires abnormal kidney structure or function present for >3 months. An acute decline in eGFR (e.g. from dehydration, contrast nephropathy, or nephrotoxic drugs) is acute kidney injury (AKI), not CKD, and is potentially reversible.
MDRD vs CKD-EPI: Which Is More Accurate?
The MDRD (Modification of Diet in Renal Disease) equation was developed in 1999 and was the first equation widely adopted for eGFR estimation. It systematically underestimates eGFR at higher values (above 60 mL/min/1.73m²), which is why many labs historically reported "≥60" rather than a specific number for MDRD eGFR. CKD-EPI 2009 improved accuracy across the full GFR range, particularly in people with near-normal kidney function. CKD-EPI 2021 maintains this accuracy without the race variable. For most clinical purposes, CKD-EPI 2021 is preferred; MDRD remains useful in populations similar to the original study cohort.
Cockcroft-Gault: Drug Dosing vs Kidney Function Assessment
The Cockcroft-Gault formula (1976) estimates creatinine clearance, not eGFR. It includes body weight, making it sensitive to muscle mass and particularly useful for drug dosing in the elderly and in patients with extremes of body weight. Drug package inserts commonly specify dosing adjustments using Cockcroft-Gault, not CKD-EPI. CG tends to overestimate GFR in obese patients (due to fat mass contributing to weight without proportional creatinine production) and underestimate GFR in very muscular individuals. Ideal body weight or adjusted body weight is often substituted for actual weight in obese patients when using CG for drug dosing.
Frequently Asked Questions
What is a normal GFR level by age?
Normal eGFR is ≥90 mL/min/1.73m² in healthy young adults. eGFR naturally declines with age — by approximately 1 mL/min/1.73m² per year after age 40. Average eGFR by decade: 20s → ~116; 30s → ~107; 40s → ~99; 50s → ~93; 60s → ~85; 70s → ~75. An eGFR that appears lower than expected for age may still represent normal ageing rather than kidney disease, especially in the absence of markers of kidney damage such as proteinuria.
What does an eGFR of 60 mean?
An eGFR of 60 mL/min/1.73m² marks the boundary between CKD Stage G2 (60–89, mildly decreased) and G3a (45–59, mildly to moderately decreased). A single value of 60 does not diagnose CKD — two measurements at least 3 months apart below 60, or evidence of kidney damage such as albuminuria, is required. At eGFR 60, kidney function is roughly 50% of the young adult average. Most people with eGFR 60 have no symptoms, as kidneys have substantial reserve.
How does creatinine relate to GFR?
Serum creatinine is an inverse proxy for GFR: as the kidneys filter less, creatinine accumulates in blood. However, creatinine production varies substantially with muscle mass, diet (meat consumption), sex, and age, which is why creatinine alone is an imprecise kidney function marker. A creatinine of 1.2 mg/dL in a young muscular male may indicate normal GFR, while the same value in a small elderly female may indicate substantially reduced kidney function. This is why GFR-estimating equations that incorporate age and sex are far more informative than creatinine alone.
Can GFR be improved?
eGFR cannot generally be improved beyond its baseline in established CKD, but progression can be slowed significantly. Key interventions include: blood pressure control (target <130/80 mmHg, or <120 mmHg in proteinuric CKD); RAAS blockade with ACE inhibitors or ARBs in proteinuric CKD; SGLT2 inhibitors (dapagliflozin, empagliflozin) which reduce intraglomerular pressure and have shown significant nephroprotection in trials; blood sugar control in diabetic nephropathy; protein restriction (0.6–0.8g/kg/day in advanced CKD); and avoidance of nephrotoxins (NSAIDs, aminoglycosides, IV contrast in high-risk patients).
What is the Schwartz formula used for?
The Schwartz formula (eGFR = 0.413 × height in cm / serum creatinine) is validated for estimating GFR in children and adolescents. It uses height because children's creatinine production scales with height better than with weight alone. The bedside Schwartz formula uses the coefficient 0.413 (updated in 2009 from the original 0.55/0.70); this revised version performs well in children with CKD. Adult formulas should not be applied to children under 18.