Pulmonology · Critical Care
Alveolar–Arterial Oxygen Gradient calculator
Enter the published formula inputs below to calculate and interpret this score.
Clinical inputs
Use local barometric pressure (760 mmHg at sea level).
Respiratory quotient; 0.8 is standard unless measured.
Result
Complete all required inputs to calculate the score.
Formula inputs
- aagradient fio2 fraction (fraction)Accepted range: 0.21 to 1
- aagradient paco2 mmhg (mmHg)Accepted range: 10 to 150
- aagradient pao2 mmhg (mmHg)Accepted range: 20 to 600
- aagradient barometric pressure mmhg (mmHg)Accepted range: 500 to 780
- aagradient water vapor pressure mmhg (mmHg)Accepted range: 40 to 50
- aagradient respiratory quotient (ratio)Accepted range: 0.7 to 1
Primary source
Alveolar gas equation as used in arterial blood gas interpretation. DOI: 10.1164/ajrccm.158.1.9711041. PMID: 9655694. Scope: calculates P(A–a)O₂ as (PB − PH₂O) × FiO₂ − PaCO₂/RQ − PaO₂ for adult arterial blood gas assessment. (1998)
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