GFR Calculator – Estimated Glomerular Filtration Rate

Written by Great Medico

Updated September 24, 2026 •2 min read

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Kidney and urology formulas often look simple but depend heavily on how the measurements were obtained. GFR Calculator – Estimated Glomerular Filtration Rate applies the exact equation built into this calculator and keeps the result tied to those inputs.

What this calculator does

GFR Calculator – Estimated Glomerular Filtration Rate uses Calculate eGFR based on…, Sex, Ethnicity, Age, and Serum creatinine to calculate legacy creatinine-based eGFR. It is built around the exact fields displayed in this plugin rather than a generic version of the topic. Where supported, it also shows CKD-EPI 2009 and MDRD so the primary result is easier to place in context. Kidney calculations often depend on paired laboratory samples, stable physiology, and the population in which the equation was validated. Acute changes in kidney function or nonstandard sampling can make an apparently precise number unreliable.

How to use it

Enter or select Calculate eGFR based on…, Sex, Ethnicity, Age, and Serum creatinine. Use the units offered by the calculator and choose the option that matches the actual clinical or timing situation. Check date entries and laboratory units before relying on the output. For paired blood, urine, or dialysis measurements, use samples and treatment data from the same collection or clinical episode when the formula requires it.

How the calculation works

This calculator currently implements two older creatinine-based eGFR equations. The CKD-EPI 2009 equation uses sex-specific κ and α terms, age, creatinine, and the historical race multiplier when “Black” is selected. The MDRD equation similarly uses creatinine, age, sex, and a historical race multiplier. The selected method is the primary output and the alternate estimate is also shown.

Example

Using the sample values prefilled in this calculator, the primary result is 81.44 mL/min/1.73m² (CKD-EPI 2009 eGFR), CKD-EPI 2009 is 81.4, and MDRD is 76.2. This worked example shows how the plugin’s own default inputs flow through the implemented method; replace them with the correct patient, laboratory, imaging, or personal values before interpreting a result.

How to interpret the result

The number represents estimated filtration normalized to 1.73 m² body surface area. Lower values generally indicate lower kidney filtration, but CKD diagnosis requires chronicity and clinical context. Because the formulas here are legacy equations, the current laboratory-reported race-free eGFR is usually more appropriate for modern care.

Limitations and notes

This is a legacy eGFR implementation. Current U.S. practice recommends the 2021 CKD-EPI creatinine equation without a race coefficient, and KDIGO 2024 supports contemporary validated GFR estimation rather than race-based adjustment. The result should therefore not be presented as the current preferred eGFR for clinical decisions; cystatin C or combined equations may also be appropriate.