Anion Gap Calculator

Calculate anion gap using common formulas (with or without potassium). Interpret using your lab’s reference range.

Inputs (mmol/L)

Sodium (Na⁺)

Chloride (Cl⁻)

Bicarbonate (HCO₃⁻)

Potassium (K⁺) (optional) Leave blank to compute AG without K.

Formula

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Enter electrolytes to calculate anion gap.

Disclaimer: For educational purposes only. Not a substitute for clinical judgment.

Reference ranges vary with assay and whether K is included. A commonly used adult range for AG (without K) is ~8–12 mmol/L, but verify locally.

High anion gap suggests unmeasured anions (e.g., lactate, ketoacids, toxins, renal failure).
Normal anion gap (hyperchloremic) metabolic acidosis suggests bicarbonate loss or impaired renal acid excretion.

Kraut JA, Madias NE. Metabolic acidosis: pathophysiology, diagnosis and management. Nat Rev Nephrol. 2010.