Anion Gap Calculator

The Anion Gap Calculator estimates the serum anion gap. Enter your sodium, chloride, and bicarbonate values to calculate your anion gap. This helps doctors check the acid-base balance in your blood. This calculator also calculates the gap with potassium if you provide it. This tool helps patients and students understand blood chemistry.

Enter sodium level between 100 and 180 (e.g., 140)
Enter chloride level between 70 and 140 (e.g., 104)
Enter bicarbonate level between 5 and 50 (e.g., 24)
Enter potassium level between 2 and 7 (optional)

This calculator is a screening tool only, not a diagnostic instrument. It is not intended to replace professional medical evaluation. Consult a healthcare provider.

What Is Anion Gap

The anion gap is a number calculated from blood test results. It measures the difference between the main positive ions and the main negative ions in your blood. This number helps doctors see if there are unusual acids in your body. A normal gap suggests a balance, while a high gap may suggest changes in how your body handles acids.

How Anion Gap Is Calculated

Formula

Anion Gap = Na⁺ − (Cl⁻ + HCO₃⁻)

Where:

  • Na⁺ = Sodium (mEq/L)
  • Cl⁻ = Chloride (mEq/L)
  • HCO₃⁻ = Bicarbonate (mEq/L)

To find the anion gap, you add the chloride and bicarbonate numbers together. Then, you subtract that sum from the sodium number. The result shows the "gap" or space left by other unmeasured particles. If potassium is used, it is added to the sodium number before subtracting the other ions. This math helps estimate the amount of unmeasured anions in the blood.

Why Anion Gap Matters

Knowing your anion gap helps doctors understand your metabolic health. It is often used to check for issues related to acid levels in the blood. This test is a key step in finding the cause of metabolic acidosis.

Why Metabolic Balance Is Important for Health

Keeping the right balance of acids and bases is vital for body functions. If the anion gap is too high, it may suggest a buildup of acids from conditions like diabetes or kidney problems. If it is too low, it may point to other issues in the blood proteins. Checking this number helps doctors screen for these hidden changes.

For Patients with Kidney Concerns

Kidneys help remove extra acid from the body. If the kidneys are not working well, acids may build up and cause a high anion gap. Monitoring this value may help doctors see how well the kidneys are filtering waste. Patients with kidney issues may need regular checks to ensure their acid levels stay safe.

Anion Gap vs Delta Gap

The anion gap checks for unmeasured acids in the blood. The delta gap is a different step that compares the change in the anion gap to the change in bicarbonate. Doctors use the delta gap to see if there is more than one issue happening at the same time with the acid levels.

Calculation logic verified using publicly available standards.

View our Accuracy & Reliability Framework →