← All Calculators

GFR Calculator — eGFR Kidney Function

Calculate estimated glomerular filtration rate (eGFR) using the CKD-EPI 2021 equation and assess kidney function.

Calculated using CKD-EPI 2021 (race-free, KDIGO-recommended). Not a substitute for medical diagnosis.

Ad

Daily nutrition made simple — vitamins, probiotics & adaptogens in one scoop.

Try AG1

CKD Stages (KDIGO)

G1Normal or high
≥ 90
G2Mildly decreased
60 – 89
G3aMildly to moderately decreased
45 – 59
G3bModerately to severely decreased
30 – 44
G4Severely decreased
15 – 29
G5Kidney failure
< 15

About This Calculator

CKD-EPI 2021 Equation

The CKD-EPI 2021 equation is the current KDIGO (Kidney Disease: Improving Global Outcomes) recommended formula. It is race-free and provides accurate estimates across all age and creatinine ranges.

Medication Dosing

Many medications are dosed based on eGFR or are contraindicated with reduced kidney function, including metformin, NSAIDs, certain antibiotics, and contrast agents.

Limitations

eGFR equations estimate kidney function — they do not directly measure it. Results may be less accurate in extreme muscle mass, malnutrition, acute kidney injury, or pregnancy.

Medical Disclaimer

This tool is for informational purposes only and does not replace medical evaluation. Abnormal kidney values should always be discussed with a healthcare provider.

Frequently Asked Questions

What is the glomerular filtration rate (GFR)?+
GFR measures how much blood the kidneys filter per minute (mL/min/1.73 m²). It is the most important marker of kidney function. Source: KDIGO.
What is a normal GFR?+
Adults: > 90 mL/min/1.73 m² is normal. 60–89 is borderline (G2). Values below 60 sustained for 3+ months indicate chronic kidney disease (CKD).
Which formula does this calculator use?+
It uses the CKD-EPI 2021 equation, the current standard for estimating GFR from serum creatinine. It is more accurate than the older MDRD formula.
Why does GFR decline with age?+
From around age 40, GFR drops about 1 mL/min/year. Hypertension, diabetes, and obesity accelerate the decline.
What are the CKD stages?+
G1 (>90), G2 (60–89), G3a (45–59), G3b (30–44), G4 (15–29), G5 (<15, kidney failure). Source: KDIGO 2012 guidelines.
How can I protect my kidneys?+
Keep blood pressure under 130/80, manage blood sugar, stay hydrated, eat low-sodium, avoid NSAIDs, stop smoking. Refer to nephrology if eGFR < 60.

Related Calculators

Alcohol Unit Calculator

Calculate your weekly alcohol consumption in UK units, grams of pure alcohol, and health risk.

Anemia Risk Calculator

Estimate your anemia risk from hemoglobin level, sex, and clinical symptoms.

Anion Gap Calculator

Calculate anion gap and classify metabolic acidosis. Includes albumin correction.

Asthma Control Test (ACT)

Calculate your ACT score — assess asthma control over the past 4 weeks.

Background

GFR Calculator — Understanding eGFR & Kidney Function

8 min