basic

Alveolar Gas Equation (PAO₂) Calculator

PAO₂ = (P_atm − P_H₂O) · FiO₂ − PaCO₂ / RQ.

Compute the alveolar partial pressure of oxygen PAO₂ from the alveolar gas equation: PAO₂ = (P_atm − P_H₂O) · FiO₂ − PaCO₂ / RQ. Defaults: sea-level barometric pressure 760 mmHg, water vapour 47 mmHg, room-air FiO₂ 0.21, normal PaCO₂ 40 mmHg, and respiratory quotient 0.8.

Priya Venkatesan By Priya Venkatesan
Published Last reviewed 1 min read

Inputs

mmHg
mmHg
mmHg

Results

Enter values and click Calculate to see results.
Was this helpful?

How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

PAO₂ = (P_atm − P_H₂O) · FiO₂ − PaCO₂ / RQ.

In depth

Compute the alveolar partial pressure of oxygen PAO₂ from the alveolar gas equation: PAO₂ = (P_atm − P_H₂O) · FiO₂ − PaCO₂ / RQ. Defaults: sea-level barometric pressure 760 mmHg, water vapour 47 mmHg, room-air FiO₂ 0.21, normal PaCO₂ 40 mmHg, and respiratory quotient 0.8.