ABG Interpreter & Acid-Base Calculator

Enter pH, PaCO₂, HCO₃⁻, and PaO₂ — get the primary disturbance, expected compensation, mixed disorder detection, and A-a gradient in seconds.

Visual Balance

Near-normal ABG

Normal-range pH can still hide compensation or competing primary processes.

Recheck

Net

0.0

Acidosis

No major acid driver

Alkalosis

No major alk driver

Read

Near-normal ABG. Compensation is not clearly classifiable from these values alone.

Compensation

No major compensation needed

Reference range check

ABG Inputs

Interpretation

Near-normal ABG. Compensation is not clearly classifiable from these values alone.

7.40

PaCO2

HCO3

Triple Dagger

Anion Gap

Delta-Delta

Osm Gap

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Add anion gap, delta gap, corrected bicarbonate, osmolar gap inputs, and the full mixed-disorder layer.

Full toolkit

Clinical Safety

Acid-base tools support interpretation but do not replace the bedside picture. Check electrolytes, lactate, renal function, and ventilation settings when the pattern looks mixed or the patient looks worse than the gas.

Acid-base interpretation steps

Step 1 — Is the pH normal? <7.35 = acidemia, >7.45 = alkalemia
Step 2 — What is the primary disturbance? ↑PaCO₂ = respiratory acidosis; ↓PaCO₂ = respiratory alkalosis; ↓HCO₃⁻ = metabolic acidosis; ↑HCO₃⁻ = metabolic alkalosis
Step 3 — Is compensation appropriate? Use Winter's formula for metabolic acidosis, or the expected pCO₂ ranges for metabolic alkalosis.
Step 4 — Check for mixed disorders. If compensation is not as expected, a second primary process may be present.
Step 5 — Calculate anion gap if metabolic acidosis is present. AG = Na⁺ − (Cl⁻ + HCO₃⁻). Normal ≈ 12 ± 2.

Winter's formula (metabolic acidosis expected compensation)

Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 (±2)

Frequently asked questions

What values does the ABG calculator need?

pH, PaCO₂ (mmHg), HCO₃⁻ (mEq/L), and optionally PaO₂ (mmHg) and FiO₂ for A-a gradient calculation.

Can it detect mixed acid-base disorders?

Yes. The interpreter checks whether compensation falls within expected ranges using standard formulas. If it doesn't, it flags a possible mixed disorder.

What is the A-a gradient and why does it matter?

The alveolar-arterial oxygen gradient helps differentiate hypoxemia causes: a normal A-a gradient suggests hypoventilation, while an elevated gradient points toward V/Q mismatch, diffusion impairment, or shunt.