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47 calculators
The widest practice area in the registry: internists use these calculations daily on the wards and in clinic — sorting out an acid-base disorder, balancing fluids and electrolytes, converting doses to body size, and staging chronic disease. Much of the toolset is arithmetic supporting a broader clinical picture, so numbers are read alongside examination, medication review, and how successive results move over days.
This page groups by clinical area, so the tools below are the ones this setting reaches for — the subject-focused view of the same calculators lives on the categories pages, the full alphabetical list collects everything in one place, and the comparison tool lines up three tools side by side when two of them look interchangeable.
Estimates glomerular filtration rate (eGFR) using the 2021 CKD-EPI creatinine equation.
NephrologyCalculates Ideal Body Weight using the Devine formula.
Internal MedicineCalculates Adjusted Body Weight using the Devine Ideal Body Weight formula.
Internal MedicineCalculates Lean Body Weight using the Boer formula.
Internal MedicineEstimates creatinine clearance (CrCl) for medication dosing using the Cockcroft-Gault equation.
NephrologyEstimates severity and prognosis of chronic liver disease and cirrhosis.
Internal MedicineCalculates the Blood Urea Nitrogen to Creatinine ratio to help differentiate causes of kidney dysfunction.
NephrologyEstimates glomerular filtration rate using the 4-variable MDRD equation.
NephrologyCalculates corrected total serum calcium adjusted for hypoalbuminemia. In hypoalbuminemia, measured total calcium is falsely low because less calcium is protein-bound; this correction estimates the physiologically active total calcium.
LaboratoryCalculates the serum anion gap using sodium, chloride, and bicarbonate. The anion gap helps differentiate high anion gap metabolic acidosis (HAGMA) from normal anion gap metabolic acidosis (NAGMA).
Internal MedicineCalculates the albumin-corrected anion gap. In hypoalbuminemia, the measured anion gap is falsely low, potentially masking a high anion gap metabolic acidosis. This correction adjusts for the albumin contribution.
Internal MedicineCalculates the estimated serum osmolality using sodium, glucose, and blood urea nitrogen (BUN). Useful in evaluating electrolyte disorders, dehydration, toxic alcohol ingestion, and calculating the osmolar gap.
Internal MedicineCalculates the osmolar gap as the difference between measured and calculated serum osmolality. An elevated osmolar gap may suggest toxic alcohol ingestion (methanol, ethylene glycol) or other osmotically active substances.
Internal MedicineEstimates basal metabolic rate using the Mifflin-St Jeor equation.
Internal MedicineEstimates basal metabolic rate using the Harris-Benedict equation.
Internal MedicineEstimates daily calorie requirement from basal metabolic rate and activity level.
Internal MedicineEstimates maintenance fluid requirement based on body weight.
Internal MedicineEstimates maintenance fluid rate using a weight-based method.
Internal MedicineEstimates free water deficit in hypernatremia. Helps quantify the amount of free water needed to restore normal sodium levels.
Internal MedicineEstimates sodium deficit for hyponatremia correction planning. Helps determine the total amount of sodium needed to raise serum sodium to a target level.
Internal MedicineCorrects serum sodium for hyperglycemia using the conventional correction factor. Hyperglycemia draws water into the extracellular space, diluting sodium; this correction estimates what sodium would be at a normal glucose level.
Internal MedicineCalculates the fractional excretion of sodium to distinguish prerenal azotemia from acute tubular necrosis.
NephrologyCalculates the fractional excretion of urea for renal evaluation, particularly useful when diuretics are present.
NephrologyCalculates the transtubular potassium gradient to assess renal potassium handling.
NephrologyCalculates the calcium-phosphate product used in renal risk assessment for vascular calcification.
NephrologyCalculates 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).
NephrologyCalculates 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.
NephrologyCalculates 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.
NephrologyCalculates 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).
NephrologyCalculates 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).
NephrologyCalculates renal free water clearance (CH₂O) from urine flow, urine osmolality, and plasma osmolality to characterize renal water handling in polyuria, hyponatremia, and hypernatremia.
NephrologyCalculates 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.
NephrologyCalculates 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.
NephrologyCalculates the total cholesterol to HDL ratio (TC/HDL), a lipid-based cardiovascular risk indicator that compares total cholesterol with the protective HDL fraction.
LaboratoryCalculates the atherogenic index of plasma (AIP), a logarithmically transformed ratio of triglycerides to HDL cholesterol that reflects the balance of atherogenic and protective lipoproteins.
LaboratoryCalculates the apolipoprotein B to apolipoprotein A1 ratio (ApoB:ApoA1), an index of the balance between atherogenic (ApoB) and anti-atherogenic (ApoA1) lipoproteins used in cardiovascular risk assessment.
LaboratoryEstimates the expected serum bicarbonate during acute or chronic respiratory acidosis and alkalosis using the Winters/Merck compensation rules, helping to identify whether a metabolic disturbance is appropriately compensated or a mixed disorder is present.
Internal MedicineCalculates the expected arterial PaCO₂ in metabolic alkalosis (PaCO₂ ≈ 40 + 0.6 × (HCO₃ − 24)) to assess whether respiratory compensation is appropriate or whether a concurrent respiratory disorder is present.
Internal MedicineEstimates low-density lipoprotein cholesterol (LDL-C) from a standard fasting lipid panel using the Friedewald equation: LDL = total cholesterol − HDL − (triglycerides / 5). Used for cardiovascular risk assessment and lipid-lowering treatment targets. Not valid when triglycerides are ≥ 400 mg/dL.
LaboratoryCalculates non-HDL cholesterol (total cholesterol minus HDL cholesterol). Non-HDL captures all atherogenic apolipoprotein B-containing lipoproteins, including LDL, VLDL, IDL, and remnants, and is a secondary lipid treatment target per ATP III guidelines.
LaboratoryCalculates the albumin to globulin ratio from serum albumin and total protein (A/G ratio = albumin / (total protein − albumin)). The ratio is used as a screening aid in the evaluation of liver disease, nephrotic syndrome, and monoclonal gammopathies, alongside the absolute albumin and globulin values.
LaboratoryCalculates the expected compensatory respiratory response to a primary metabolic acidosis: expected PaCO2 = 1.5 × HCO3 + 8 ± 2 mmHg. It is used to determine whether the respiratory response is appropriate, inadequate (respiratory acidosis), or excessive (respiratory alkalosis).
Internal MedicineCalculates the anion gap delta ratio to evaluate the acid-base response in a high anion gap metabolic acidosis: ΔAG/ΔHCO3 = (measured anion gap − 12) / (24 − measured HCO3). It helps identify mixed acid-base disorders such as a concurrent non-anion gap acidosis or metabolic alkalosis.
Internal MedicineCalculates 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.
NephrologyAdjusts measured serum magnesium for hypoalbuminemia. When serum albumin is low, measured total magnesium is falsely reduced because less magnesium is bound to proteins. This correction estimates the physiologically relevant magnesium level.
LaboratoryCalculates the gradient between serum albumin and ascitic fluid albumin to classify ascites as portal hypertensive (SAAG ≥1.1 g/dL) or non-portal hypertensive (SAAG <1.1 g/dL). First-line diagnostic tool for ascites workup.
GastroenterologyObjective prognostic assessment of liver function using serum albumin and bilirubin. Primarily validated in hepatocellular carcinoma (HCC) for stratifying prognosis and guiding treatment decisions.
Gastroenterology