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GFR Calculator | Estimate eGFR and Classify CKD Stage

Estimates kidney function using the 2021 CKD-EPI creatinine equation. Enter your serum creatinine, age, sex, and race, and the tool calculates your estimated glomerular filtration rate (eGFR) in mL/min/1.73 m², then classifies the result into the corresponding chronic kidney disease (CKD) stage.

Last updated: June 2026 · Free · No sign-up required

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

CKD stages by eGFR:

Stage	eGFR (mL/min/1.73m2)	Kidney function
G1	90+	Normal
G2	60–89	Mildly reduced
G3a/G3b	30–59	Moderately reduced
G4	15–29	Severely reduced
G5	<15	Kidney failure

monitor_weight A starting point, not a diagnosis

This calculator gives you the same number a clinician would compute by hand from your inputs. It is informational, never a substitute for a doctor. If a result surprises you, write it down and discuss it at your next appointment — that conversation is the goal, not a verdict from a webpage.

science Built from peer-reviewed formulas

Every health calculator on CalcaTools uses an equation from the WHO, NIH, ACOG, CDC, or a published peer-reviewed paper. The exact citation is in the "Formula & methodology" section. We re-check sources quarterly and update the page when guidance changes — the "Last reviewed" date is at the top.

volunteer_activism Designed for real people

Health calculations only help if you can actually use them. We use plain-English labels (no jargon), accept both metric and US units, and show what a "normal" range looks like alongside your result — so you understand what the number means, not just what it is.

lock Private by design

Your weight, height, age, pregnancy details, and any other health input never leave your browser. Calculations run client-side; nothing is logged or stored on our side. We don't want your medical data — we just want the formula to work for you.

Interpretation guide

eGFR inputs:

Input	Role
Serum creatinine	Primary marker (mg/dL)
Age	Function declines with age
Sex	Adjusts the equation
2021 update	Removed the race coefficient

lightbulb Worked example

Let's say you are using the GFR Calculator. Estimates kidney function using the 2021 CKD-EPI creatinine equation. Enter your serum creatinine, age, sex, and race, and the tool calculates your estimated glomerular filtration rate (eGFR) in Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula 2021 CKD-EPI uses serum creatinine, age, and sex (no race term) to estimate GFR per 1.73m2 and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: 2021 CKD-EPI uses serum creatinine, age, and sex (no race term) to estimate GFR per 1.73m2

The GFR Calculator is built on a well-established calculation method. It uses the formula 2021 CKD-EPI uses serum creatinine, age, and sex (no race term) to estimate GFR per 1.73m2 to turn your inputs into a reliable result. Estimates kidney function using the 2021 CKD-EPI creatinine equation. Enter your serum creatinine, age, sex, and race, and the tool calculates your estimated glomerular filtration rate (eGFR) in mL/min/1.73 m², then The steps are shown on the page so you can follow the reasoning from input to output.

Estimated GFR gauges how well the kidneys filter blood, derived from serum creatinine, age, and sex using the 2021 CKD-EPI equation (which removed the earlier race coefficient). Results are normalized to a standard body surface area of 1.73 m2. Lower eGFR indicates reduced kidney function and maps to CKD stages. This is a screening estimate — diagnosis and management require a clinician and may use confirmatory testing.

Authoritative source: National Kidney Foundation

Frequently asked questions

What is eGFR?

The GFR Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Estimates kidney function using the 2021 CKD-EPI creatinine equation. Enter your serum creatinine, age, sex, and race, and the tool calculates your estimated glomerular filtration rate (eGFR) in mL/min/1.73 m², then classifies the result into the There is no limit on usage, and it works on any device.

What is a normal GFR?

Normal GFR is generally 90–120 mL/min/1.73m² for healthy young adults, declining gradually with age — many people over 60 run 60–89, which can still be normal for their age. Chronic kidney disease staging begins below 60 for 3+ months (stage 3), with lower stages indicating more advanced disease. GFR is interpreted by a doctor in context with creatinine, age, and other health factors.

Why was the race coefficient removed in 2021?

The 2021 CKD-EPI equation removed the race coefficient because race is a social construct, not a biological variable, and the coefficient was based on outdated assumptions that could misclassify kidney function in Black patients, delaying referrals and care. The 2021 equation uses serum creatinine, age, and sex only, giving more equitable estimates. It is now the recommended standard.

What affects creatinine levels?

Serum creatinine reflects muscle mass and kidney excretion: it is higher in muscular individuals and athletes, lower in older adults and those with less muscle; it rises after intense exercise, high-protein meals, and creatine supplements, and falls with pregnancy and severe liver disease. Dehydration and some medications (NSAIDs, certain antibiotics) also raise it. The GFR estimate inherits these influences, which is why doctors repeat tests and interpret in context.

Is this a diagnosis?

No — the calculator provides an eGFR estimate from a single creatinine value, which is a screening and staging aid, not a diagnosis. Confirming chronic kidney disease requires repeat measurements over at least 3 months plus other markers (like urine albumin), and management decisions require a clinician. Use the result to inform a conversation with your doctor, never to self-diagnose.

What does the GFR Calculator do?

What formula does the GFR Calculator use?

The GFR Calculator applies the standard formula: 2021 CKD-EPI uses serum creatinine, age, and sex (no race term) to estimate GFR per 1.73m2. The tool walks through each step of the calculation so you can verify the numbers yourself.

Is the GFR Calculator free and private?

Yes — the GFR Calculator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.

How accurate is the GFR Calculator?

The GFR Calculator applies the standard formula: 2021 CKD-EPI uses serum creatinine, age, and sex (no race term) to estimate GFR per 1.73m2. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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