P/F Ratio Calculator
PaO₂/FiO₂ ratio with Berlin ARDS severity and SpO₂/FiO₂.
Enter your values to see the result.
Berlin definition of ARDS: mild 200–300, moderate 100–200 and severe ≤ 100 mmHg, with PEEP ≥ 5 cmH₂O and a compatible clinical picture. For education and clinical decision support only. Results do not replace professional judgment, local protocols or the product information, so always verify doses and values before acting on them.
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Clear instructions
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How to use the P/F Ratio Calculator
PaO₂/FiO₂ ratio with Berlin ARDS severity and SpO₂/FiO₂.
- 1 Enter PaO₂ in mmHg or kPa and the FiO₂.
- 2 Tick whether the patient is on PEEP or CPAP of at least 5 cmH₂O.
- 3 Read the P/F ratio and ARDS category.
Example and practical tips
A PaO₂ of 85 mmHg on 50% oxygen gives a P/F ratio of 170, in the moderate ARDS range.
Further reading
Frequently asked questions
What is a normal P/F ratio?
About 400–500 mmHg in healthy lungs. Below 300 indicates impaired oxygenation.
Does a low P/F ratio mean ARDS?
Not on its own. ARDS also needs acute onset, bilateral opacities and no full explanation by heart failure.
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