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GFR Calculator

Free eGFR calculator using the 2021 CKD-EPI race-free equation. Enter creatinine, age, and sex to get your kidney function, CKD stage, normal ranges by age, and what your number means.

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Example — Age 50 years, Serum Creatinine 1.0:

eGFR (2021 CKD-EPI)

68.6 mL/min/1.73m²

An eGFR of 68.6 (60–89) is common and only indicates kidney disease if accompanied by other markers like protein in the urine. Doctors look for a confirmed trend over 3+ months, not one value.

CKD Stage

Stage 2 — Mildly decreased kidney function

Kidney Function Level

Mildly reduced

Formula

2021 CKD-EPI Creatinine Equation (race-free)

Important Medical Notice

This eGFR is an estimate. Clinical decisions should consider the full clinical context including trends over time, other lab values, and patient history. Confirm with a healthcare provider.

The formula

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

SCr
Serum Creatinine
κ (kappa)
Sex-specific coefficient
eGFR
Estimated Glomerular Filtration Rate
CKD Stage
Chronic Kidney Disease Stage
Age
Age (years)

Worked example — Age 50 years, Serum Creatinine 1.0

eGFR (2021 CKD-EPI) = 68.6 mL/min/1.73m²

Full explanation ↓

How GFR Calculator Works

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

The 2021 CKD-EPI equation estimates glomerular filtration rate from serum creatinine without a race coefficient. The original 2009 and 2012 equations included a race factor that was removed in 2021 when evidence showed it systematically overestimated kidney function in Black patients, potentially delaying care.

SCr
Serum Creatinine — A waste product from muscle metabolism. Elevated levels indicate reduced kidney filtration.
κ (kappa)
Sex-specific coefficient — 0.7 for females, 0.9 for males. Adjusts the creatinine ratio by sex.
eGFR
Estimated Glomerular Filtration Rate — Volume of blood filtered per minute, normalized to 1.73m² body surface area. The standard measure of kidney function.
CKD Stage
Chronic Kidney Disease Stage — Stage 1 (≥90) through Stage 5 (<15). Lower eGFR = more advanced disease.
Age
Age (years) — eGFR naturally declines with age. The formula applies a 0.9938^Age factor, meaning eGFR decreases ~0.6% per year even without kidney disease.

Source: 2021 CKD-EPI Creatinine Equation — developed by the Chronic Kidney Disease Epidemiology Collaboration, published in the New England Journal of Medicine (Inker et al., 2021), and recommended as the clinical standard by the National Kidney Foundation and the American Society of Nephrology.

CKD-EPI 2021 equation estimates eGFR from serum creatinine, age, and sex without race coefficient

How to Use

  1. Enter your serum creatinine value from a recent lab test.
  2. Select the correct unit (mg/dL is standard in the US, μmol/L in most other countries).
  3. Enter your age and sex.
  4. Review your eGFR and CKD stage.
  5. Discuss results with your healthcare provider — this is a screening estimate, not a diagnosis.

Quick Reference

eGFR ≥ 90Stage 1 — normal or high
eGFR 60–89Stage 2 — mildly decreased
eGFR 45–59Stage 3a — mild to moderate
eGFR 30–44Stage 3b — moderate to severe
eGFR 15–29Stage 4 — severely decreased
eGFR < 15Stage 5 — kidney failure
CKD diagnosiseGFR < 60 for 3+ months

Common Uses

  • •Kidney disease screening — use eGFR from the 2021 CKD-EPI race-free equation to assess kidney function and detect early-stage chronic kidney disease
  • •CKD staging and monitoring — track eGFR trends over time to determine CKD stage and guide treatment planning with a nephrologist
  • •Medication safety review — healthcare providers check eGFR before prescribing renally cleared medications (e.g., metformin, some antibiotics) to adjust dosing appropriately
  • •Pre-operative assessment — eGFR is routinely checked before surgery to assess kidney function and anesthetic risk, especially in patients with diabetes or hypertension

Understanding the Result

The Glomerular Filtration Rate (GFR) is the best overall measure of kidney function. The 2021 CKD-EPI equation is the current clinical standard recommended by the National Kidney Foundation and the American Society of Nephrology. It replaced older equations that included race coefficients, which were found to overestimate GFR in Black individuals and contribute to disparities in kidney disease diagnosis and treatment. eGFR below 60 mL/min/1.73m² for 3+ months indicates chronic kidney disease.

An eGFR of 15 or lower indicates kidney failure, requiring dialysis or transplant consideration. eGFR is affected by age (declines naturally after ~40), hydration status, muscle mass, certain medications, and acute illness — a single abnormal result should be confirmed with repeat testing. For example, a 65-year-old with an eGFR of 68 might be experiencing normal age-related decline rather than kidney disease, while a 30-year-old with the same eGFR would likely need further investigation.

Serum creatinine, the lab value used in the equation, is itself affected by muscle mass: a bodybuilder may have elevated creatinine (and thus appear to have lower eGFR) simply because they have more muscle mass producing more creatinine as a metabolic waste product. This is why cystatin C-based GFR estimates are sometimes used as a confirmatory test in people with very high or very low muscle mass. Other factors that can temporarily lower eGFR include dehydration, high-protein meals before blood draws, recent strenuous exercise, and certain medications like NSAIDs (ibuprofen, naproxen) and ACE inhibitors.

Worked Examples

A 45-year-old woman with serum creatinine of 0.8 mg/dL

creatinine = 0.8 · age = 45 · sex = female · creatinineUnit = mgdl

eGFR ≈ 102 mL/min/1.73m² — Stage 1

Creatinine of 0.8 is comfortably within the normal female range (0.6–1.1 mg/dL), and at 45 the age penalty (0.9938^45 ≈ 0.76 of the base value) still leaves filtration in the normal band.

A 70-year-old man with serum creatinine of 1.3 mg/dL

creatinine = 1.3 · age = 70 · sex = male · creatinineUnit = mgdl

eGFR ≈ 57 mL/min/1.73m² — Stage 3a

The same creatinine in a 40-year-old would produce an eGFR near 69. Age drives much of the difference, which is why doctors interpret borderline values like this in context — and confirm with a repeat test and urine albumin before diagnosing CKD.

A 30-year-old male bodybuilder with creatinine of 1.4 mg/dL

creatinine = 1.4 · age = 30 · sex = male · creatinineUnit = mgdl

eGFR ≈ 66 mL/min/1.73m² — appears Stage 2

High muscle mass produces more creatinine, deflating the eGFR estimate without any kidney problem. This is a textbook case for a confirmatory cystatin C test, which is independent of muscle mass.

Frequently Asked Questions

Why was the race coefficient removed from GFR equations?
The race coefficient was removed in 2021 after studies showed it systematically overestimated GFR in Black patients, leading to delayed diagnosis of chronic kidney disease, lower transplant referral rates, and worse outcomes. The 2021 CKD-EPI equation is race-free and provides more equitable care.
What is a normal eGFR?
An eGFR of 90 mL/min/1.73m² or above is considered normal. However, eGFR naturally declines with age — a value of 75 in a 70-year-old may be normal aging rather than disease. A single eGFR reading should be interpreted in context of your age, trends over time, and other health factors.
What happens at each CKD stage?
Stage 1–2: Often asymptomatic, managed with monitoring and lifestyle. Stage 3: Begin seeing a nephrologist, manage blood pressure and protein intake. Stage 4: Prepare for renal replacement therapy (dialysis or transplant). Stage 5: Kidney failure — dialysis or transplant is needed. Early detection significantly improves outcomes.

Pro Tips

  • →Hydrate normally before your blood draw — dehydration concentrates creatinine and can knock 5–10 points off your eGFR.
  • →Avoid intense exercise for 48 hours and large protein/creatine doses for 24 hours before testing; both temporarily raise creatinine.
  • →Track your trend, not single values. Print or save this result and compare against your next lab — a stable 75 matters less than a 90→75→62 decline.
  • →If you take NSAIDs (ibuprofen, naproxen) regularly, mention it when discussing your eGFR — they reduce kidney blood flow and lower the reading.
  • →Ask your lab for a urine albumin-to-creatinine ratio (uACR) alongside eGFR — CKD staging requires both, and uACR often catches damage before eGFR drops.

Limitations to Know

  • •This calculator uses the creatinine-only 2021 CKD-EPI equation. It is less accurate at extremes of muscle mass (bodybuilders, amputees, frail elderly, paralysis) — a cystatin C-based estimate is preferred in those cases.
  • •eGFR is normalized to a standard 1.73m² body surface area; for drug dosing at very high or low body sizes, clinicians may de-normalize the value.
  • •The equation is validated for adults 18+ only. Pediatric GFR uses the separate Bedside Schwartz equation.
  • •A single eGFR cannot diagnose CKD — diagnosis requires reduced eGFR or kidney damage markers persisting for at least 3 months.
  • •Results are unreliable during acute kidney injury, pregnancy, or rapidly changing creatinine — the equation assumes steady-state kidney function.

Sources

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TheCalcUniverse. "GFR Calculator — 2021 CKD-EPI eGFR with CKD Stage (Race-Free)." TheCalcUniverse, 2026, https://thecalcuniverse.com/health/gfr-calculator/. Accessed July 27, 2026.

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