eGFR and GFR Calculator (CKD-EPI 2021)

This calculator estimates eGFR with the race-free CKD-EPI 2021 equation from age, sex, and serum creatinine, and it also works as a GFR calculator. It returns the result in mL/min/1.73m² and shows the matching CKD stage.

What Is eGFR?

Estimated glomerular filtration rate (eGFR) is a calculated measure of how much blood the glomeruli filter each minute, standardised to a body surface area of 1.73m². It is the standard measure for staging chronic kidney disease. eGFR estimates glomerular filtration, whereas creatinine clearance estimates clearance for drug dosing. For a plain-language primer, see what is eGFR?

GFR, eGFR and Measured GFR

Glomerular filtration rate (GFR) is the volume of blood the kidneys filter each minute, the single most useful number for describing overall kidney function. Because it cannot be measured directly in routine care, it is estimated from a blood marker, almost always serum creatinine: that estimate is the eGFR this calculator returns. Measured GFR (mGFR) uses an external filtration marker, such as iohexol or inulin, and is the gold standard, but it is slow, costly, and rarely needed. It is reserved for situations where an exact value matters, for example evaluating a potential living kidney donor or dosing a narrow-therapeutic-index drug when the estimate is in doubt.

How the CKD-EPI 2021 Equation Works

The CKD-EPI 2021 creatinine equation uses age, sex, and serum creatinine, applying sex-specific coefficients (κ and α) and an age term. It deliberately omits any race coefficient. Read the full CKD-EPI 2021 equation explained.

The equation has the form eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × (1.012 if female). In this formula, Scr is serum creatinine in mg/dL; κ is 0.7 for women and 0.9 for men; and α is −0.241 for women and −0.302 for men. The two power terms split the creatinine value at the κ threshold so the curve fits both lower and higher creatinine ranges, and the 0.9938^age term applies the gradual decline in filtration that accompanies ageing. The female multiplier of 1.012 corrects for the lower average creatinine production in women at a given filtration rate. The result is reported per 1.73m² of body surface area, the standardised adult value.

Worked Example

Take a 55-year-old woman with a serum creatinine of 1.1 mg/dL. Her κ is 0.7, so Scr/κ = 1.1 / 0.7 ≈ 1.57. Because that ratio exceeds 1, the min(Scr/κ, 1) term equals 1 (so its α power contributes a factor of 1), and the max term is 1.57^−1.200. Combining the max term, the 0.9938^55 age factor, and the female multiplier of 1.012 with the constant 142 gives an eGFR of roughly 55 mL/min/1.73m². That value falls in the G3a band, which would prompt confirmation on a repeat sample and a check of urine albumin before staging chronic kidney disease.

Serum Creatinine Units

The CKD-EPI 2021 equation expects serum creatinine in mg/dL. If your laboratory reports in µmol/L, divide by 88.4 to convert to mg/dL first (for example, 97 µmol/L ÷ 88.4 ≈ 1.1 mg/dL). Entering the wrong unit shifts the result substantially, so confirm the unit on the report. The creatinine unit converter handles this conversion.

Why the 2021 Update Removed Race

The earlier 2009 equation applied a separate multiplier for Black patients. In 2021 a joint NKF-ASN task force recommended a race-free equation for all adults, because race is a social rather than biological category.

What Is a Normal eGFR by Age?

An eGFR of 90 mL/min/1.73m² or higher is typical, and the value declines gradually with age:

See normal eGFR by age for detail, and what a low eGFR means.

What Does My eGFR Number Mean?

Each guide below explains one result: its KDIGO category, the serum creatinine that produces it at different ages for men and women, and any renal dosing cutoffs that sit at that number.

• eGFR 90 (G1)
• eGFR 75 (G2)
• eGFR 60 (G2)
• eGFR 55 (G3a)
• eGFR 50 (G3a)
• eGFR 45 (G3a)
• eGFR 40 (G3b)
• eGFR 35 (G3b)
• eGFR 30 (G3b)
• eGFR 25 (G4)
• eGFR 20 (G4)
• eGFR 15 (G4)

eGFR vs Creatinine Clearance

Use eGFR for staging kidney disease and creatinine clearance for drug dosing. They are not interchangeable: read CrCl vs eGFR for the full comparison. The two values use different units (mL/min/1.73m² versus mL/min) and different reference points. Creatinine clearance tends to read slightly higher because the kidney tubules secrete a small amount of creatinine in addition to filtering it. In a very large or very small person the indexed eGFR must be de-indexed to absolute mL/min before the two numbers can be compared meaningfully.

How to Use Your eGFR in Practice

A single eGFR is a starting point for interpretation rather than a diagnosis. If the result is below 60 mL/min/1.73m², the usual next steps are to repeat the test after about three months to confirm the change is sustained and to check urine albumin to grade kidney damage. The usual next steps also include a review of medications and contributing conditions with a clinician. A stable eGFR above 60 with no albuminuria is generally reassuring. Because the estimate depends on serum creatinine, a sudden drop in eGFR alongside a rapidly rising creatinine points to a non-steady state, where the equation should not be trusted until the level settles. Use the number to start a conversation with a clinician rather than to make a treatment decision on its own.

eGFR and CKD Stages (G1-G5)

eGFR defines the KDIGO GFR categories from G1 to G5. A single eGFR is a snapshot; chronic kidney disease requires the reduction or kidney damage to persist for at least three months. Read the result against the band below:

An eGFR in the G1 or G2 range is not automatically normal: staging also depends on albuminuria and on whether the change is sustained. See CKD stages explained for the full GFR-and-albuminuria grid. Two people can share an identical GFR yet face very different risk if one has heavy albuminuria and the other has none, which is why a GFR result is most useful alongside a urine test.

What Changes GFR Over Time

Glomerular filtration rate falls when fewer or less-efficient glomeruli are filtering blood, which can happen gradually in chronic kidney disease or abruptly in acute kidney injury. The most common drivers of a sustained decline are diabetes and high blood pressure, which together account for most chronic kidney disease. Age also matters: filtration declines slowly across adulthood, so a value that would be low in a young adult can be expected in an older one. Short-term swings in the estimated value, by contrast, often reflect changes in serum creatinine rather than true filtration. A high-protein meal or strenuous exercise can nudge creatinine up and the estimate down without any real change in kidney function.

When eGFR Is Preferred, and When It Is Not

Use eGFR (CKD-EPI 2021) as the first-line estimate for staging kidney disease, screening, and tracking kidney function over time. For renal drug dosing, many drug labels were validated against creatinine clearance from the Cockcroft-Gault equation, so confirm which value a given drug expects. When a creatinine-based estimate is likely to mislead (at the extremes of muscle mass), a cystatin C estimate can confirm the result.

Limitations and Edge Cases

Because eGFR is derived from serum creatinine, anything that changes creatinine production or handling independently of filtration can skew the estimate:

• Low muscle mass (frailty, amputation, paralysis, advanced age): less creatinine is produced, so eGFR reads falsely high and can mask reduced filtration.
• High muscle mass or high-protein intake: more creatinine is produced, so eGFR may read falsely low in an otherwise healthy person.
• Acute kidney injury or any non-steady state: when creatinine is rising or falling rapidly, eGFR equations assume a stable level and are not valid.
• Pregnancy: filtration rises physiologically and the equations are not validated, so eGFR is not used to stage kidney function in pregnancy.
• Extremes of body size: because eGFR is indexed to 1.73m², it must be de-indexed to absolute mL/min before comparing it with a Cockcroft-Gault CrCl in a very large or small person.

Related Kidney Calculators

• Creatinine clearance calculator (Cockcroft-Gault)
• MDRD GFR calculator
• Cystatin C eGFR calculator
• CKD-EPI 2009 calculator: for comparison with older results