eGFR Calculator (Kidney Function)

Which equation does this tool use?

It uses the race-free CKD-EPI 2021 creatinine equation: 142 multiplied by min(Scr/κ, 1) raised to α, by max(Scr/κ, 1) raised to −1.200, by 0.9938 raised to the power of age, and by 1.012 if female. The formula was checked against the National Kidney Foundation page at kidney.org/professionals/ckd-epi-creatinine-equation-2021. The figures built into this tool are those constants.

Why is there no race input?

The 2021 CKD-EPI creatinine equation was published without a race term, so there is nothing to select. The National Kidney Foundation lists it as the race-free refit of the equation. This tool takes only creatinine, age and sex.

Why do the results differ from the 2009 equation?

The 2021 equation uses different constants (142 instead of 141, an age term of 0.9938 per year, different α and an exponent of −1.200) and has no race multiplier, so the same creatinine, age and sex can give a different figure. For a 45-year-old man with creatinine 1.0 mg/dL, an earlier version of this page printed 90.1 and this version prints 94.6. A laboratory report may use either equation, so compare like with like.

What are κ and α, and how do they change the result?

κ is a sex-specific creatinine reference value: 0.7 for female and 0.9 for male. α is the exponent applied when creatinine divided by κ is below 1: −0.241 for female and −0.302 for male. When the ratio is 1 or higher, the exponent is −1.200 for both sexes. At a ratio of exactly 1 both terms equal 1, so the two branches meet without a jump.

Which units does it expect, and what inputs are rejected?

Serum creatinine must be entered in mg/dL, and the answer is in mL/min/1.73 m². There is no unit switch, so convert micromoles per litre first. A zero or negative creatinine returns an error, as does an age below 18 or above 110. Nothing is silently substituted.

What is the “CKD Stage” line?

It is a built-in label chosen by comparing the computed eGFR with fixed cut-offs of 90, 60, 45, 30 and 15 (G1 to G5, the usual KDIGO bands), together with a short descriptive phrase. It uses the eGFR value alone. It does not look at urine protein, duration or any other test, so it is not a diagnosis.

Is the result valid for children, pregnancy or acute illness?

The tool is limited to adults, and the equation assumes a steady creatinine level. It has no inputs for muscle mass, diet, medicines that affect creatinine, pregnancy, dialysis or rapidly changing kidney function, so the figure can be misleading in those settings. Pediatric and other equations are not included.

Can I use this to make treatment or dosing decisions?

No. This page is general information, not medical advice, and a clinician governs any decision. It does not replace clinical judgement, your laboratory’s own reported eGFR or advice from the prescriber or pharmacist, and it must not be used to decide a patient’s treatment or medicine doses.