Age

Creatinine (mg/dL)

Sex assigned at birth

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General estimate for planning only — not medical advice. Consult a doctor about your specific situation.

Calculation details

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eGFR results for different ages and creatinine levels — A 60 percent creatinine rise takes eGFR from 90 to 36.

Method & verification

How This Tool Works

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Calculation Method

Computes eGFR from Age, Creatinine and Sex assigned at birth.

Site methodology

BoringToolsKit methodology and verification standard

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Assumptions to Verify

These tools provide general estimates for planning and education only.
They are not medical advice and not a substitute for a qualified healthcare professional.
Always consult your doctor or another healthcare provider about your specific situation.

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Worked example: the 2021 equation, step by step

Take a 45-year-old woman with a creatinine of 1.0 mg/dL. The equation first rescales creatinine: 1.0 divided by 0.7 gives 1.4286. Because that is above 1, only the second term applies, raised to the fixed exponent -1.200: 1.4286 to the power -1.200 equals 0.6518. The age term is 0.9938 raised to 45, which equals 0.7559. The female multiplier is 1.012.

Multiply it out: 142 x 0.6518 = 92.56; 92.56 x 0.7559 = 69.97; 69.97 x 1.012 = 70.8. The result rounds to 71 mL/min/1.73m2, which lands in stage G2 (mildly decreased), since it sits between 60 and 89.

Notice how the spline split works: at creatinine exactly 0.7 (the female reference value) the first term equals 1, so the estimate is driven purely by the -1.200 slope plus age. One number shows how sharply the slope bites: a 60-year-old man at the same 1.0 mg/dL scores 90, but raise his creatinine to 1.6 and he drops to 36, a G3b result, from a 60 percent creatinine increase.

Where the estimate bends and who it can mislead

The 2021 refactor removed the race coefficient but kept the creatinine ceiling problem: at low muscle mass, eGFR runs high. A frail 82-year-old woman weighing 48 kg with a creatinine of 0.8 gets an estimate near 73, yet her measured clearance is typically 15 to 25 percent lower than that, because creatinine production scales with muscle, not just kidney function. This matters for drug dosing: metformin and DOAC labels are keyed to renal function, so an inflated estimate can push a dose up.

Two edge cases the input validation will not flag. First, creatinine between 0 and about 0.4 is physiologically implausible in adults and usually means a lab reporting unit slip (umol/L typed as mg/dL); the calculator will happily compute a near-perfect score from it. Second, the spline kink at 0.7 (women) and 0.9 (men) means estimates are least precise right where G2 and G3a meet: a creatinine shift of 0.05 mg/dL around the kink can move the stage boundary itself.

In practice, guidelines call a result below 60 'chronic kidney disease' only after it repeats below 60 on tests at least 3 months apart. A single estimate of 58 in a well-hydrated 70-year-old is often just noise; the same number twice, six months apart, is a diagnosis conversation.