How does the ABG Calculator work?

The ABG Calculator takes pH, PaCO2, and HCO3- values and applies standard acid-base analysis rules to determine whether the patient has acidosis or alkalosis, whether it is respiratory or metabolic in origin, and whether compensation is present.

What is the normal range for arterial blood gas values?

Normal ranges are: pH 7.35-7.45, PaCO2 35-45 mmHg, and HCO3- 22-26 mEq/L. The ABG Calculator uses these reference ranges to classify results.

Can the ABG Calculator detect mixed disorders?

Yes. When the ABG Calculator identifies abnormalities in both respiratory and metabolic components that do not fit a single disorder pattern, it classifies the result as a mixed disorder.

No. All calculations happen in your browser; nothing is sent to a server.

ABG Calculator - CalculatorBox

How to Use ABG Calculator

The ABG Calculator helps clinicians and students analyze arterial blood gas results quickly and accurately. Enter the three key parameters from the lab report, and the ABG Calculator instantly classifies the acid-base disturbance.

Enter pH — Input the arterial blood pH value (normal range: 7.35-7.45).
Enter PaCO2 — Input the partial pressure of carbon dioxide in mmHg (normal range: 35-45 mmHg).
Enter HCO3- — Input the bicarbonate level in mEq/L (normal range: 22-26 mEq/L).
Review the result — The ABG Calculator displays the acid-base status, type (respiratory, metabolic, or mixed), and compensation analysis.

The ABG Calculator provides a structured interpretation that includes a text summary explaining the clinical significance of the findings.

Formula & Theory - ABG Calculator

The ABG Calculator uses a systematic approach to arterial blood gas interpretation:

Step 1: Assess pH

pH < 7.35 → Acidosis
pH > 7.45 → Alkalosis
7.35 ≤ pH ≤ 7.45 → Normal

Step 2: Determine Primary Disorder

Condition	Respiratory Indicator	Metabolic Indicator
Acidosis	PaCO2 > 45 mmHg	HCO3- < 22 mEq/L
Alkalosis	PaCO2 < 35 mmHg	HCO3- > 26 mEq/L

Step 3: Evaluate Compensation

For metabolic acidosis, the expected respiratory compensation is calculated using Winter’s formula:

Expected PaCO2 = 1.5 × HCO3- + 8 ± 2

For metabolic alkalosis:

Expected PaCO2 = 0.7 × ΔHCO3- + 40

For respiratory acidosis (acute vs chronic):

Acute:  ΔHCO3- = 1 mEq/L per 10 mmHg ↑ PaCO2
Chronic: ΔHCO3- = 3.5 mEq/L per 10 mmHg ↑ PaCO2

Assumptions and Limits

The ABG Calculator is an educational and clinical decision-support tool. It assumes standard physiological compensation mechanisms. Always correlate results with clinical presentation, patient history, and additional laboratory data. This calculator does not replace professional medical judgment.

Use Cases for ABG Calculator

The ABG Calculator is valuable in many clinical and educational settings:

Emergency medicine — Rapidly interpret ABG results in acute care settings to guide ventilation and fluid management decisions.
Critical care — Monitor acid-base balance in ICU patients on mechanical ventilation using the ABG Calculator for trend analysis.
Medical education — Students and residents use the ABG Calculator to practice and verify their ABG interpretation skills.
Pulmonology — Assess respiratory function and compensation in patients with chronic lung diseases.
Nephrology — Evaluate metabolic acidosis or alkalosis in patients with renal impairment.
Anesthesiology — Monitor acid-base status during surgical procedures and post-operative recovery.

From bedside emergencies to exam preparation, the ABG Calculator delivers clear, structured interpretations that support confident clinical decision-making.

ABG Calculator