GFR Calculator

CKD-EPI 2021 Kidney Function Estimator

Enter your age, sex, and serum creatinine level to estimate your glomerular filtration rate (eGFR).

Parameters

Age

Sex

Male Female

Serum Creatinine (mg/dL)

Estimated GFR

mL/min/1.73m²

Enter your details to see your estimated GFR.

Validation Error

Please provide a valid age and creatinine level to proceed.

Understanding Glomerular Filtration Rate (GFR)

GFR estimates how well your kidneys filter waste from your blood. This calculator uses the CKD-EPI 2021 creatinine equation — the current standard, race-free formula recommended by major kidney health organizations.

What GFR Measures

GFR reflects the volume of blood filtered by the kidneys per minute, normalized to a standard body surface area (1.73m²).

Serum Creatinine

Creatinine is a waste product from muscle metabolism — higher blood levels generally indicate reduced kidney filtering capacity.

Why the Race-Free Update

The 2021 CKD-EPI equation removed a race coefficient present in earlier versions, following recommendations to improve equity in kidney disease diagnosis.

One Piece of the Picture

Kidney health assessment also considers urine albumin, blood pressure, and trends over time — not GFR alone.

The CKD-EPI 2021 Equation

\[ eGFR = 142 \times \min\left(\frac{Scr}{\kappa}, 1\right)^{\alpha} \times \max\left(\frac{Scr}{\kappa}, 1\right)^{-1.200} \times 0.9938^{Age} \times 1.012 \text{ [if female]} \]

Where Scr is serum creatinine in mg/dL, κ is 0.7 (female) or 0.9 (male), and α is -0.241 (female) or -0.302 (male).

CKD Stages

Stage	eGFR (mL/min/1.73m²)	Description
G1	≥90	Normal or high
G2	60-89	Mildly decreased
G3a	45-59	Mildly to moderately decreased
G3b	30-44	Moderately to severely decreased
G4	15-29	Severely decreased
G5	<15	Kidney failure

Important Limitations

Not a diagnosis: A single eGFR reading is a screening estimate — CKD diagnosis requires sustained reduced GFR (typically over 3+ months) or other markers like albuminuria.
Muscle mass affects creatinine: Very muscular or very frail individuals can have creatinine levels that don't perfectly reflect true kidney function.
Requires an actual lab value: This tool needs a real serum creatinine measurement — it cannot estimate kidney function without one.

Key Takeaways

CKD-EPI 2021 is the current clinical standard. It's the race-free equation now recommended by kidney health organizations.
Higher eGFR means better kidney function. The scale runs opposite to creatinine — higher creatinine means lower eGFR.
Trends matter more than a single value. Kidney function assessment typically tracks eGFR over multiple readings.
Consult a professional. GFR is a critical kidney-function marker — this estimate is not a diagnosis; always review your results with a physician or nephrologist alongside an actual lab creatinine test.

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