A-a Gradient

Name: A-a Gradient
Creator: Daniel Diaz-Gil, MD
Keywords: A-a gradient, alveolar-arterial, PAO2, PaO2, oxygen, gradient, hypoxemia, pulmonology, ABG, pediatric

Calculates alveolar-arterial oxygen gradient to evaluate causes of hypoxemia with age-adjusted normal values

Clinically Verified· 5 tests

For educational and informational purposes only. Verify all results before clinical application.

Age *

years

FiO2 (%) *

PaO2 (mmHg) *

mmHg

PaCO2 (mmHg) *

mmHg

Atmospheric Pressure (mmHg)

mmHg

Atmospheric pressure in mmHg. Standard sea level = 760 mmHg. Adjust for altitude if applicable.

References

Helmholz HF Jr. The abbreviated alveolar air equation. Chest. 1979;75(6):748.[DOI]

Reviewed by Daniel Diaz-Gil, MD · Last updated March 2026

Medical disclaimer

This tool is for educational and informational purposes only. It is not a substitute for professional clinical judgment. Always independently verify results before making clinical decisions.

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Kendig's Disorders of the Respiratory Tract in ChildrenComprehensive pediatric pulmonology reference~$180via Amazon Pediatric Pulse OximeterFingertip pulse oximeter suitable for pediatric patients~$30via Amazon