GFR Calculator

Q: What is GFR and why is it important?

GFR (Glomerular Filtration Rate) measures how well your kidneys filter waste from the blood, expressed in mL/min/1.73m². A normal GFR is above 90. Lower values indicate reduced kidney function and may signal chronic kidney disease (CKD). It is the single best overall index of kidney function.

Q: What is the difference between CKD-EPI 2021 and MDRD equations?

The CKD-EPI 2021 equation is the latest standard recommended by KDIGO. It removed the race coefficient for a more equitable approach and is more accurate at higher GFR values (above 60). The MDRD equation is older, less accurate above GFR 60, and still used in some labs. CKD-EPI 2021 is the preferred formula for most clinical settings.

Q: What do the CKD stages mean?

CKD stages classify kidney function severity: Stage G1 (GFR ≥90) means normal function with other signs of kidney damage; Stage G2 (60–89) is mildly decreased; Stage G3a (45–59) is mild-to-moderate decrease; Stage G3b (30–44) is moderate-to-severe; Stage G4 (15–29) is severely decreased; Stage G5 (GFR <15) is kidney failure requiring dialysis or transplant.

Q: How accurate is an online GFR calculator?

Online GFR calculators use the same validated equations that clinical labs use and are highly accurate when correct creatinine values are entered. However, eGFR is an approximation—actual GFR can differ in people with unusual muscle mass, diet, or certain medications. Always consult a healthcare provider for clinical interpretation.

Q: What is a normal creatinine level?

Normal serum creatinine is approximately 0.7–1.2 mg/dL for adult males and 0.5–1.0 mg/dL for adult females. Creatinine is a waste product from normal muscle metabolism filtered by the kidneys. Higher values may indicate reduced kidney function, though levels can vary with muscle mass, age, and hydration status.

Calculate estimated glomerular filtration rate using the CKD-EPI 2021, CKD-EPI 2009, MDRD and Cockcroft-Gault equations. See your CKD stage, compare the results across formulas, and get kidney health context for each.

Free to useNo sign-up requiredUpdated Mar 2026

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⚡ Quick Examples

Serum Creatinine

mg/dL

Creatinine Unit

Age (18–120 years)

Biological Sex

Weight Optional (for Cockcroft-Gault)

Weight Unit

Height Optional (for BSA-adjusted CG)

Height Unit

Embed GFR Calculator Widget

About GFR Calculator

Glomerular Filtration Rate (GFR) is the best overall measure of kidney function. It estimates how much blood passes through the glomeruli — tiny filters in your kidneys — each minute. GFR is measured in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73m²).

How to Calculate Your GFR

Enter your serum creatinine: Enter your serum creatinine level from a recent blood test. You can input it in mg/dL or µmol/L.
Provide your age and sex: Enter your age in years and select your biological sex, as GFR equations use sex-specific coefficients.
Optional: Enter weight and height: For the Cockcroft-Gault equation, enter your weight. Height is optional and helps calculate body surface area for adjusted results.
Review your results: View your estimated GFR from multiple equations, your CKD stage classification, and personalized health insights with an interactive kidney gauge.

What Is GFR (Glomerular Filtration Rate)?

Healthy kidneys filter about 120–130 mL/min/1.73m². As kidney function declines, GFR decreases, leading to waste buildup in the blood. Chronic Kidney Disease (CKD) is defined as having a GFR below 60 for three months or more, or having kidney damage markers (such as protein in urine) even with a normal GFR.

GFR Equations Explained

CKD-EPI 2021 (Recommended)

The CKD-EPI 2021 equation is the current standard recommended by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN). It removed the race variable present in the 2009 version, providing a single equation that is more equitable and equally accurate across populations.

CKD-EPI 2021:

$$\text{eGFR} = 142 \times \min(S_{cr}/\kappa, 1)^{\alpha} \times \max(S_{cr}/\kappa, 1)^{-1.200} \times 0.9938^{\text{Age}} \times F$$

Where: $\kappa$ = 0.7 (F) or 0.9 (M); $\alpha$ = −0.241 (F) or −0.302 (M); F = 1.012 (F) or 1 (M); $S_{cr}$ = serum creatinine in mg/dL

CKD-EPI 2009

The predecessor to the 2021 equation, CKD-EPI 2009 included a race coefficient. While still found in some labs, it is being phased out in favor of the 2021 version. This calculator shows the race-neutral version of the 2009 equation for comparison purposes.

MDRD (Modification of Diet in Renal Disease)

Developed in 1999 and updated in 2006, the MDRD equation was the standard for years. It is less accurate at GFR values above 60 and tends to underestimate kidney function in healthy individuals. Many labs have now switched to CKD-EPI.

MDRD:

$$\text{eGFR} = 175 \times S_{cr}^{-1.154} \times \text{Age}^{-0.203} \times F$$

Where F = 0.742 for females

Cockcroft-Gault

The Cockcroft-Gault equation, published in 1973, estimates creatinine clearance (CrCl) rather than GFR. It requires the patient's weight and produces results in mL/min (not adjusted for body surface area). It is still commonly used for drug dosing in clinical pharmacology.

Cockcroft-Gault:

$$\text{CrCl} = \frac{(140 - \text{Age}) \times \text{Weight(kg)}}{72 \times S_{cr}} \times F$$

Where F = 0.85 for females. Result in mL/min (not BSA-adjusted).

CKD Stages Based on GFR

Stage	GFR (mL/min/1.73m²)	Kidney Function	Description
G1	≥ 90	Normal or High	Kidney damage with normal filtration; may have proteinuria
G2	60 – 89	Mildly Decreased	Mild loss; usually detected through lab tests
G3a	45 – 59	Mild-to-Moderate	Moderate loss; may begin showing symptoms
G3b	30 – 44	Moderate-to-Severe	Complications more likely; specialist referral recommended
G4	15 – 29	Severely Decreased	Preparing for renal replacement therapy
G5	< 15	Kidney Failure	Dialysis or transplant needed

What Affects GFR?

Age: GFR naturally declines with age, roughly 1 mL/min/year after age 30.
Sex: Males tend to have slightly higher GFR due to greater muscle mass and creatinine production.
Muscle mass: Muscular individuals may have higher creatinine levels without impaired kidney function.
Diet: High-protein diets (especially red meat) can temporarily increase creatinine levels.
Medications: Some drugs (ACE inhibitors, NSAIDs, certain antibiotics) can affect GFR or creatinine levels.
Hydration: Dehydration can temporarily reduce GFR.
Acute illness: Infections, surgeries, or injuries can cause temporary GFR decline.

When to See a Doctor

You should consult a healthcare provider if your eGFR is below 60, if you notice sudden changes in urination, persistent swelling in your legs or ankles, unexplained fatigue, or if you have risk factors for kidney disease such as diabetes, high blood pressure, or a family history of kidney problems.

Frequently Asked Questions

What is GFR and why is it important?

GFR (Glomerular Filtration Rate) measures how well your kidneys filter waste from the blood, expressed in mL/min/1.73m². A normal GFR is above 90. Lower values indicate reduced kidney function and may signal chronic kidney disease (CKD). It is the single best overall index of kidney function.

What is the difference between CKD-EPI 2021 and MDRD equations?