Anion Gap Calculator
Anion Gap Calculator is a health and wellness calculator that helps you calculate anion gap values from your input data. The formula used is: AG = Na − (Cl + HCO3); Corrected = AG + 2.5 × (4.0 − albumin). Enter values using the units shown next to each input field (e.g. kg, cm, years).
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Diagnostic aid for acid-base assessment. Requires clinical interpretation.
Formula
AG = Na − (Cl + HCO3); Corrected = AG + 2.5 × (4.0 − albumin)
- Anion Gap Calculator gives you a fast estimate using your inputs and updates instantly when you change any value.
- Formula: AG = Na − (Cl + HCO3); Corrected = AG + 2.5 × (4.0 − albumin)
- Input definitions: • Sodium: serum Na⁺ in mmol/L • Chloride: serum Cl⁻ in mmol/L • Bicarbonate: serum HCO₃⁻ in mmol/L • Albumin (optional): serum albumin in g/dL, used to correct the gap
- Manual method: write down each input, apply the formula step by step, then compare your manual result with the calculator output.
- Enter values using the units shown next to each input field (e.g. kg, cm, years).
- This calculator uses widely accepted health formulas and returns screening estimates only. It does not replace a diagnosis from a qualified healthcare professional.
- Compare your result with published reference ranges. Values outside the normal range warrant a conversation with your doctor.
- Practical tip: test a low, medium, and high scenario to understand sensitivity before making decisions.
Example Calculation
Inputs
- Sodium: 140 mmol/L
- Chloride: 104 mmol/L
- Bicarbonate: 24 mmol/L
- Albumin (optional): 4 g/dL
With Na 140, Cl 104 and HCO₃ 24, the anion gap is 140 − (104 + 24) = 12 mmol/L. At a normal albumin of 4.0 g/dL the correction is zero, so the corrected gap is also 12 — the upper edge of normal.
Frequently asked questions
What is the anion gap?
It estimates unmeasured anions in the blood: AG = Na − (Cl + HCO₃). It helps classify metabolic acidosis as high- or normal-gap.
Why correct for albumin?
Albumin is a major unmeasured anion, so low albumin lowers the apparent gap. The correction adds 2.5 mmol/L for every 1 g/dL the albumin is below 4.0.
What is a normal anion gap?
Roughly 8–12 mmol/L, though reference ranges vary by lab and whether potassium is included.
What units should I enter?
Enter sodium, chloride, and bicarbonate in mmol/L and albumin in g/dL.
How do I interpret a high gap?
A raised gap points to causes such as ketoacidosis, lactic acidosis, kidney failure, or toxins — it needs clinical evaluation.
How can I verify the calculation manually?
Use the displayed formula and work through the numbers step by step. If your manual result differs slightly, check rounding and unit conversions first.
Can I use this for planning and budgeting?
Yes. Run best-case, expected, and worst-case inputs to compare outcomes and make safer planning decisions.
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