GFR Calculator

Q: What is a normal GFR?

A normal glomerular filtration rate (GFR) is about 90 to 120 mL/min/1.73m2. GFR estimates how many milliliters of blood the kidneys filter each minute, and it is calculated from serum creatinine, a muscle waste product that builds up in the blood when the kidneys filter less well.

Q: What GFR indicates kidney disease?

A GFR below 60 mL/min/1.73m2 for three months or more indicates chronic kidney disease (CKD). A GFR of 60 to 89 can also count as CKD stage G2 when there are other signs of kidney damage, such as protein in the urine. A single low reading is not a diagnosis.

Q: What does a creatinine of 1.1 mean for a 55-year-old woman?

For a 55-year-old woman, a serum creatinine of 1.1 mg/dL gives an estimated GFR of about 59 mL/min/1.73m2 using the CKD-EPI 2021 equation, which falls in CKD stage G3a. It is a screening estimate: high muscle mass, a meat-heavy diet and some medicines can raise creatinine without kidney damage.

Q: Which eGFR formula is most accurate?

The CKD-EPI 2021 equation is the current standard recommended by KDIGO guidelines. It replaced the 2009 version and removed the race coefficient, following 2021 NKF and ASN recommendations. MDRD is less accurate at higher GFR values, and Cockcroft-Gault is older but still used for drug dosing.

Estimate glomerular filtration rate using CKD-EPI 2021, MDRD, and Cockcroft-Gault formulas. Includes pediatric Schwartz formula.

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What is Glomerular Filtration Rate?

GFR measures how much blood your kidneys filter per minute, expressed in mL/min/1.73m² (normalized to body surface area). It is the primary indicator of kidney function and is used to diagnose and stage chronic kidney disease (CKD).

GFR Formulas

CKD-EPI 2021 (Recommended)

The current standard from KDIGO guidelines. This race-free equation was adopted after the 2021 NKF-ASN task force recommendation:

eGFR = 142 × min(S_Cr/κ, 1)^α × max(S_Cr/κ, 1)^−1.200 × 0.9938^Age × (1.012 if female)

Where κ = 0.7 (female) or 0.9 (male), and α = −0.241 (female) or −0.302 (male).

MDRD (Modification of Diet in Renal Disease)

The 4-variable MDRD formula is less accurate above 60 mL/min but still widely used:

eGFR = 175 × S_Cr^−1.154 × Age^−0.203 × (0.742 if female)

Cockcroft-Gault

The oldest formula, still used for drug dosing. Requires body weight and is not normalized to body surface area:

CrCl = ((140 − Age) × Weight) / (72 × S_Cr) × (0.85 if female)

Bedside Schwartz (Pediatric)

For children under 18:

eGFR = 0.413 × Height(cm) / S_Cr

CKD Stages

Stage	GFR (mL/min/1.73m²)	Description
G1	≥ 90	Normal or high function
G2	60–89	Mildly decreased
G3a	45–59	Mild to moderate decrease
G3b	30–44	Moderate to severe decrease
G4	15–29	Severely decreased
G5	< 15	Kidney failure (dialysis or transplant may be needed)

Factors Affecting GFR

Age: GFR naturally declines about 1 mL/min/year after age 30
Diet: High protein intake temporarily increases GFR; creatine supplements raise serum creatinine without kidney damage
Muscle mass: Muscular individuals may have higher creatinine, underestimating GFR
Medications: NSAIDs, ACE inhibitors, and some antibiotics can affect GFR
Hydration: Dehydration temporarily lowers GFR

When to See a Doctor

This calculator provides estimates only and should not replace medical advice. See a healthcare provider if your estimated GFR is below 60, or if you have symptoms like persistent fatigue, swelling, changes in urination, or foamy urine.

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Frequently Asked Questions

What is a normal GFR?

A normal glomerular filtration rate (GFR) is about 90 to 120 mL/min/1.73m2. GFR estimates how many milliliters of blood the kidneys filter each minute, and it is calculated from serum creatinine, a muscle waste product that builds up in the blood when the kidneys filter less well.

What GFR indicates kidney disease?

A GFR below 60 mL/min/1.73m2 for three months or more indicates chronic kidney disease (CKD). A GFR of 60 to 89 can also count as CKD stage G2 when there are other signs of kidney damage, such as protein in the urine. A single low reading is not a diagnosis.

What does a creatinine of 1.1 mean for a 55-year-old woman?

For a 55-year-old woman, a serum creatinine of 1.1 mg/dL gives an estimated GFR of about 59 mL/min/1.73m2 using the CKD-EPI 2021 equation, which falls in CKD stage G3a. It is a screening estimate: high muscle mass, a meat-heavy diet and some medicines can raise creatinine without kidney damage.

Which eGFR formula is most accurate?

The CKD-EPI 2021 equation is the current standard recommended by KDIGO guidelines. It replaced the 2009 version and removed the race coefficient, following 2021 NKF and ASN recommendations. MDRD is less accurate at higher GFR values, and Cockcroft-Gault is older but still used for drug dosing.