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21 calculators
The broadest clinical category, covering acid-base analysis, fluid and electrolyte management, body weight estimation, metabolic assessment, and organ function scoring. Tools include anion gap and delta ratio calculations for metabolic acidosis, corrected sodium for hyperglycaemia, serum osmolality and osmolar gap for toxic ingestion workup, and Winter's formula for expected respiratory compensation. Fluid management tools include maintenance fluids, sodium deficit, free water deficit, and calorie requirement calculators. Body weight tools (IBW, adjusted BW, lean body weight, BMR, Harris-Benedict) support drug dosing and nutritional planning. Organ function scores include Charlson Comorbidity Index and Child-Pugh. These are workhorses of daily inpatient and outpatient medicine — most are most accurate when used alongside clinical assessment rather than in isolation.
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.
Calculates 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 severity and prognosis of chronic liver disease and cirrhosis.
Internal MedicineCalculates 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 MedicineEstimates 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 MedicineCalculates 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 MedicineThe Charlson Comorbidity Index (Charlson 1987) predicts one-year and ten-year mortality from a weighted count of 19 comorbidities (weights 1, 2, 3, and 6) plus an age adjustment (per decade over 40, 1994). Higher scores indicate greater comorbidity burden and lower estimated ten-year survival, with wide application as a case-mix adjustment in outcomes research and clinical prognostication.
General Medicine