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Health Calculators

Anion Gap Calculator

Verified formula Updated Jun 2026 Private — runs on your device

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mEq/L
mEq/L
mEq/L
Verified formula Private

Anion gap

12.0

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Anion Gap Calculator

The Anion Gap Calculator works out your anion gap in an instant. Enter sodium (na⁺), chloride (cl⁻) and bicarbonate (hco₃⁻) and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the sodium (na⁺).
  2. Enter the chloride (cl⁻).
  3. Enter the bicarbonate (hco₃⁻).
  4. Read off your anion gap — the calculator updates automatically, with no button to press.

Formula

The Anion Gap Calculator uses the formula:

Anion gap = Sodium (Na⁺) - (Chloride (Cl⁻) + Bicarbonate (HCO₃⁻))

Worked example

For example, with sodium (na⁺) of 140 mEq/L, chloride (cl⁻) of 104 mEq/L and bicarbonate (hco₃⁻) of 24 mEq/L, the anion gap is 12.0.

Inputs used
Sodium (Na⁺) 140 mEq/L
Chloride (Cl⁻) 104 mEq/L
Bicarbonate (HCO₃⁻) 24 mEq/L
Results
Anion gap 12.0

Results are estimates for educational use, not professional advice.

Frequently asked questions

It is the difference between measured cations and anions in blood: sodium minus the sum of chloride and bicarbonate.

A typical range is about 8 to 12 mEq/L, though reference ranges vary by laboratory and method.

A high anion gap can point to certain types of metabolic acidosis, helping narrow down a diagnosis.

Some formulas add potassium. This calculator uses the common version with sodium only.

The Anion Gap Calculator uses the formula: Anion gap = Sodium (Na⁺) - (Chloride (Cl⁻) + Bicarbonate (HCO₃⁻)). For example, with sodium (na⁺) of 140 mEq/L, chloride (cl⁻) of 104 mEq/L and bicarbonate (hco₃⁻) of 24 mEq/L, the anion gap is 12.0.

Enter the sodium (na⁺). Enter the chloride (cl⁻). Enter the bicarbonate (hco₃⁻). Read off your anion gap — the calculator updates automatically, with no button to press.

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