eGFR Calculator

If your blood report shows a creatinine value, you probably noticed the lab also prints something called “eGFR” — or worse, your report flags kidney concern without explaining it. eGFR (estimated Glomerular Filtration Rate) is the single best number doctors use to judge how well your kidneys filter waste from your blood, and it drives the staging of chronic kidney disease worldwide. Our free eGFR calculator uses the CKD-EPI 2021 equation — the current reference standard from the Chronic Kidney Disease Epidemiology Collaboration, endorsed by KDIGO (Kidney Disease: Improving Global Outcomes) — to compute your eGFR from age, sex, and serum creatinine.

What Is eGFR?

Your kidneys contain about a million tiny filters (glomeruli) each. Glomerular filtration rate measures how many millilitres of blood they filter per minute, standardised to 1.73 m² of body surface area. Because measuring GFR directly requires injecting tracer substances, doctors estimate it from serum creatinine — a waste product of muscle metabolism — plus age and sex, which predict muscle mass.

The CKD-EPI 2021 equation (race-free, the current standard) is:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age × (1.012 if female)
where κ = 0.7 (female) / 0.9 (male), α = −0.241 (female) / −0.302 (male), and Scr is serum creatinine in mg/dL.

CKD Stage	eGFR (mL/min/1.73m²)	Meaning
G1	90+	Normal kidney 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	Below 15	Kidney failure

How to Use the eGFR Calculator

1. Enter your age and select your sex (the equation adjusts for typical muscle mass).
2. Enter serum creatinine in mg/dL (it’s printed on your kidney function test — KFT/RFT report).
3. Click Calculate — your eGFR and CKD stage appear.
4. Interpret with your doctor, not from this page alone — creatinine fluctuates with dehydration, heavy meals, muscle injury, and some medicines.

Worked Example

A 40-year-old man with serum creatinine 1.0 mg/dL: κ = 0.9, α = −0.302. min(1.0/0.9, 1) = 1, max = 1.111. eGFR = 142 × 1 × 1.111^−1.2 × 0.9938⁴⁰ ≈ 142 × 0.881 × 0.780 ≈ 97.6 mL/min/1.73m² — stage G1, normal.

Important Notes

• This is a screening estimate, not a diagnosis. Only a doctor with your full history can diagnose kidney disease.
• Pakistan carries a heavy CKD burden — diabetes and hypertension are its leading causes here, so anyone with either should be tested regularly.
• Very muscular people, bodybuilders, and people with amputations can get misleading creatinine-based eGFR — mention this to your doctor.
• Single readings can wobble: repeat tests over weeks matter more than one number.

Medical disclaimer: this tool provides an estimate for information only and is not medical advice; always discuss your results with a qualified doctor.

Frequently Asked Questions

What is a normal eGFR?

90 or above is considered normal in adults, though GFR naturally declines about 1 mL/min/year after age 40. 60–89 can be normal for an older adult without other kidney signs — context matters.

Why does eGFR use age and sex?

Because creatinine comes from muscle, and muscle mass varies by age and sex. The equation uses them as proxies for how much creatinine your body “should” be making.

Can eGFR be wrong?

Yes — dehydration, recent meat-heavy meals, creatine supplements, intense exercise, and drugs like trimethoprim shift creatinine. Your doctor interprets it alongside urine tests (ACR) and trends.

How often should diabetics check kidney function?

KDIGO and diabetes guidelines recommend at least annual eGFR and urine albumin checks for people with diabetes — more often if already abnormal.

eGFR vs creatinine clearance — which is better?

eGFR (CKD-EPI) is the standard for staging CKD. Creatinine clearance (Cockcroft-Gault) is older and still used for some drug dosing. Our creatinine clearance calculator covers that one.

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