Kidney Function Calculators
Assessing kidney function means looking at glomerular filtration, tubular handling of solutes and protein loss in urine. This category covers equation-based eGFR, creatinine clearance from a 24-hour urine collection, fractional excretions and measures of proteinuria and albuminuria, for laboratories, clinicians, students and teachers.
Glomerular filtration and creatinine
Use these to estimate GFR from serum creatinine with CKD-EPI 2021 or MDRD. The group also measures creatinine clearance from a 24-hour urine and adjusts creatinine in jaundiced patients.
Estimate GFR using the CKD-EPI 2021 equation.
Open calculatorEstimate GFR using the MDRD equation (IDMS, without race).
Open calculatorCalculate measured creatinine clearance from a timed urine collection, corrected to 1.73 m², and the Cockcroft-Gault estimate.
Open calculatorCheck whether bilirubin may have affected creatinine, based on the laboratory method.
Open calculator
Fractional excretion and tubular handling
Use these in the workup of acute kidney injury (FENa and FEUrea) and to assess renal uric acid excretion. All three compare serum and urine levels of a solute with serum and urine creatinine.
Calculate FENa and read it against the ranges published by Espinel (1976).
Open calculatorCalculate FEUrea and read it against the 35% and 50% cutoffs (Carvounis, 2002).
Open calculatorCalculate FEUA and, with collection volume and time, uric acid clearance in mL/min.
Open calculator
Proteinuria and albuminuria
Use these to quantify protein loss in a 24-hour urine, estimate it from a spot sample with the protein-to-creatinine ratio, or calculate the urine albumin-to-creatinine ratio (UACR).
Calculate urine protein excretion over 24 hours and see the KDIGO proteinuria category.
Open calculatorCalculate the urine protein-to-creatinine ratio, estimate 24-hour proteinuria and see the KDIGO category.
Open calculatorCalculate the urine albumin-to-creatinine ratio and see the KDIGO albuminuria category.
Open calculator
Choosing the right calculator
For adults with stable creatinine, CKD-EPI 2021 is the first choice: it uses creatinine, age and sex, and no race coefficient. MDRD remains available for comparison with older reports and studies, but it tends to be less accurate when filtration is preserved. Measured creatinine clearance from a 24-hour urine helps when equations fit poorly, such as at extremes of muscle mass, after amputation or on unusual diets; the same calculator also gives the Cockcroft-Gault (1976) estimate.
FENa and FEUrea answer the same question in acute kidney injury. Diuretics affect FENa, so FEUrea is often preferred in that setting. For urine protein, a 24-hour collection quantifies total loss, the protein-to-creatinine ratio avoids a timed collection and UACR measures albumin specifically.
Caveats and limitations
eGFR equations assume creatinine is at steady state. In acute kidney injury, when creatinine is rising or falling quickly, eGFR does not reflect current filtration. CKD-EPI and MDRD were developed in adults and do not apply to children.
Check the creatinine unit, mg/dL or µmol/L, and the assay. Current equations rely on IDMS-traceable methods, and bilirubin can interfere with some assays. For fractional excretion, serum and urine must be collected at the same time. In a 24-hour clearance, incomplete collection is the main source of error: record the total volume and make sure the first void is discarded at the start.
Results support laboratory interpretation and teaching. They do not stage kidney disease or guide treatment without clinical assessment.
Frequently asked questions
What is the difference between eGFR and measured creatinine clearance?
eGFR is calculated from serum creatinine plus details such as age and sex, with no urine collection. Measured clearance uses serum creatinine and a 24-hour urine and depends on a complete collection. It is useful when equations are likely to be off.
Why does CKD-EPI 2021 not use race?
The 2021 version was refitted to remove the race coefficient used in earlier versions, which rested on a social rather than biological category. The equation estimates GFR from creatinine, age and sex.
When should I use FEUrea instead of FENa?
Diuretics increase urinary sodium excretion and can distort FENa. In patients on diuretics, FEUrea is used as an alternative because urea handling is less affected by these drugs. Both results need clinical context to be interpreted.
Spot protein-to-creatinine ratio or 24-hour urine protein?
A spot ratio avoids the errors of a timed collection and is practical for follow-up. A 24-hour urine quantifies total loss directly but requires a complete collection. The choice follows local protocol and the clinical question.
A support tool for educational purposes; it does not replace clinical assessment.