Anion Gap Calculator

Calculate anion gap for acid-base balance assessment and metabolic disorder diagnosis

Last updated: 2026-05-13

Anion Gap Calculation

Enter serum electrolyte values to calculate anion gap

Advanced Mode

Enable advanced calculation features including Delta Gap, albumin-corrected AG, and Delta Ratio analysis

Calculation Formula

Unit

Serum Sodium (Na+) (mEq/L)*

Serum Chloride (Cl-) (mEq/L)*

Serum Bicarbonate (HCO3-) (mEq/L)*

Formula

AG = Na+ - (Cl- + HCO3-)

Normal Range: 8-16 mEq/L

Medical Reminder

Important Note

This calculator is for reference by medical professionals only and cannot replace professional medical diagnosis and treatment.

Medical Consultation

If anion gap is abnormal, please consult a doctor promptly for further examination and treatment.

Calculation History

No calculation records

Anion gap formulas

The anion gap estimates the difference between routinely measured serum cations and anions. Albumin correction is included because low albumin can lower the observed gap.

Standard AG = Na+ - (Cl- + HCO3-)
Extended AG = (Na+ + K+) - (Cl- + HCO3-)
Albumin-corrected AG = AG + 2.5 x (4.0 - albumin g/dL)

Na+: Serum sodium; Measured in mmol/L or mEq/L.
Cl-: Serum chloride; Measured in mmol/L or mEq/L.
HCO3-: Serum bicarbonate; Measured in mmol/L or mEq/L.
K+: Serum potassium; Optional in the extended formula.
albumin: Serum albumin; Used for optional correction when available.

How this anion gap calculator works

This tool performs electrolyte arithmetic and presents common interpretation ranges. It cannot diagnose the cause of an acid-base disorder.

Validate that the required electrolytes are present and in plausible numeric ranges.
Calculate the selected standard or potassium-inclusive anion gap formula.
If albumin is provided, apply the common correction of 2.5 mmol/L for every 1 g/dL albumin below 4.0 g/dL.
Compare the result with broad reference ranges and show advanced delta calculations when available.

Important notes

Reference intervals vary by lab method, albumin level, patient population, and local reporting conventions.
The result should be interpreted with pH, pCO2, lactate, ketones, renal function, medication history, and the full clinical picture.
Urgent symptoms, severe electrolyte abnormalities, or suspected toxic ingestion require immediate professional care.

Sources

Medical disclaimer

This anion gap calculator is for education and clinical arithmetic support only. It is not a diagnosis tool and must not replace professional medical evaluation, laboratory review, or emergency care.

Medical Disclaimer

This tool is for educational purposes only and should not be used as a substitute for professional medical diagnosis or advice.