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21 calculators
Kidney function estimation, renal replacement therapy adequacy, electrolyte handling, and acute kidney injury assessment. Core tools include the CKD-EPI 2021 and MDRD GFR equations for estimated glomerular filtration rate, Cockcroft-Gault for creatinine clearance (drug dosing), and 24-hour urine creatinine clearance. AKI staging uses the KDIGO criteria. Tubular function assessment covers fractional excretion of sodium, urea, calcium, phosphate, and uric acid, plus the transtubular potassium gradient. Fluid and electrolyte tools include the urine anion gap, osmolal gap, electrolyte-free water clearance, and calcium-phosphate product. Dialysis adequacy is assessed via Kt/V. These calculators are most valuable when interpreted alongside clinical context — fractional excretion values are unreliable with recent diuretic use, and GFR equations have reduced accuracy at extreme muscle mass.
Every tool in this domain is linked below, each with its own formula, inputs, and interpretation notes. Starting from the clinical area instead of the subject? The same calculators are grouped on the specialties pages, the full alphabetical list collects everything in one place, and the comparison tool lines up three tools side by side.
Estimates glomerular filtration rate (eGFR) using the 2021 CKD-EPI creatinine equation.
Internal MedicineEstimates creatinine clearance (CrCl) for medication dosing using the Cockcroft-Gault equation.
Internal MedicineCalculates the Blood Urea Nitrogen to Creatinine ratio to help differentiate causes of kidney dysfunction.
Internal MedicineEstimates glomerular filtration rate using the 4-variable MDRD equation.
Internal MedicineCalculates urine albumin-to-creatinine ratio (ACR) for CKD screening and staging.
NephrologyCalculates the fractional excretion of sodium to distinguish prerenal azotemia from acute tubular necrosis.
Internal MedicineCalculates the fractional excretion of urea for renal evaluation, particularly useful when diuretics are present.
Internal MedicineCalculates the transtubular potassium gradient to assess renal potassium handling.
Internal MedicineCalculates the calcium-phosphate product used in renal risk assessment for vascular calcification.
Internal MedicineCalculates the fractional excretion of uric acid (FEUA) to help distinguish prerenal azotemia from intrinsic renal injury in acute kidney injury, and to assess uric acid handling (e.g., SIADH, tumor lysis, Fanconi syndrome).
Internal MedicineCalculates the fractional excretion of phosphate (FEP) to localize the cause of hypophosphatemia: a high FEP indicates renal phosphate wasting, whereas a low FEP suggests redistribution or extrarenal loss.
Internal MedicineCalculates the fractional excretion of calcium (calcium–creatinine clearance ratio, CCCR) to help distinguish familial hypocalciuric hypercalcemia (FHH) from primary hyperparathyroidism in patients with hypercalcemia and non-suppressed PTH.
Internal MedicineCalculates the renal failure index (RFI), a classic urinary index that uses urine sodium relative to the urine:plasma creatinine ratio to help distinguish prerenal azotemia from acute tubular necrosis (ATN).
Internal MedicineCalculates the urine osmolal gap — the difference between measured and estimated urine osmolality — to detect unmeasured osmoles in the urine (e.g., ethylene glycol, mannitol, or other toxins).
Internal MedicineCalculates renal free water clearance (CH₂O) from urine flow, urine osmolality, and plasma osmolality to characterize renal water handling in polyuria, hyponatremia, and hypernatremia.
Internal MedicineCalculates urinary electrolyte-free water clearance (EFWC) from urine flow and urinary/plasma sodium and potassium. It is used to distinguish renal from extrarenal water losses and to guide fluid therapy in dysnatremia.
Internal MedicineCalculates the urine protein-to-creatinine ratio (UPCR) from a spot urine sample to estimate 24-hour proteinuria for CKD detection, monitoring, and nephrotic range proteinuria screening.
Internal MedicineCalculates creatinine clearance from a 24-hour urine collection using urine creatinine, serum creatinine, and 24-hour urine volume. It is the classic timed-collection estimate of GFR.
NephrologyCalculates the urine anion gap: UAG = (urine sodium + urine potassium) − urine chloride. It is used to distinguish renal from extrarenal (gastrointestinal) causes of a normal anion gap (hyperchloremic) metabolic acidosis with hypokalemia and normal renal function.
Internal MedicineCalculates single-pool Kt/V (spKt/V) for hemodialysis adequacy using the Daugirdas second-generation formula. KDOQI defines a minimum delivered spKt/V of 1.2 per treatment for patients treated three times weekly, with a target of 1.4.
NephrologyClassifies acute kidney injury (AKI) severity using the KDIGO 2012 criteria based on serum creatinine changes and urine output. The highest applicable stage is assigned when multiple criteria are met.
Nephrology