Biology & Medicine Tool

Anion Gap

Calculate the serum anion gap with optional potassium inclusion. This page combines the live calculator with the underlying formula or method, a worked example and practical study notes.

Study Tools / Biology & Medicine / Anion Gap
Clinical note: Anion-gap conventions and reference ranges vary with the laboratory and whether potassium is included. Use the selected formula consistently.
Interactive calculator
Calculate Anion Gap

What Is the Anion Gap?

Calculate the serum anion gap with optional potassium inclusion. The calculator is paired with the governing relationship so the numerical output stays connected to the concept you are studying.

Use Anion Gap to test worked problems, inspect how changing an input changes the output, and verify your own arithmetic before returning to the underlying concept.

Formula or Method

Formula / method
AG = Na⁺ − (Cl⁻ + HCO₃⁻) | AG(K⁺) = Na⁺ + K⁺ − (Cl⁻ + HCO₃⁻)

For Na=140, Cl=104 and HCO₃=24 mEq/L, AG=12 mEq/L without potassium. Reference ranges depend on the laboratory method and convention, so the numerical calculation should not be interpreted in isolation. Keep units and conventions consistent with the problem statement and with the options shown in the calculator.

How to Use the Calculator

  1. Read the input labels and enter the values requested by the problem, exercise or sequence.
  2. Check units, signs, angle mode, date convention, population/sample options or other settings before calculating.
  3. Compare the result with the displayed formula or method and the worked example below.
  4. Round only at the stage required by the question, course or reference convention.

Worked Example

Example: For Na=140, Cl=104 and HCO₃=24 mEq/L, AG=12 mEq/L without potassium.

Common Mistakes

Why It Matters for Students

This tool is useful when a biological or physiologic relationship needs a fast numerical or sequence-based check. Keep the variables, units and assumptions visible while practising.

Reference ranges depend on the laboratory method and convention, so the numerical calculation should not be interpreted in isolation. The interactive calculator is designed to make that relationship easier to verify while studying, not to replace the worked reasoning in a textbook or question stem.

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These pages are part of the same Study Tools system. For the complete collection, open the 2,420-tool NexaMed Study Tools hub.

Frequently Asked Questions

What is the anion gap used for?
The Anion Gap applies the relationship or method shown on this page to the inputs you provide. It is intended as a practical study and reference tool and keeps the calculation method visible beside the interactive result.
What formula or method does the anion gap use?
For Na=140, Cl=104 and HCO₃=24 mEq/L, AG=12 mEq/L without potassium.
How do I use the anion gap?
Enter the requested values, check units or options, and calculate. Then compare the result with the displayed method, worked example and notes on the page. Use the same conventions required by your course, textbook or problem statement.
Calculation source: This page uses the NexaMed Prep Study Tools engine and the same tool definition used by the main interactive hub. Formula descriptions are presented for educational reference; follow the conventions, units and assumptions required by your course, textbook or examination.