PF Ratio Calculator
Calculate PaO₂/FiO₂ ratio, oxygenation category and respiratory severity bands directly in your browser.
Hit Calculate to see your oxygenation zone
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Your explanation appears here
PF ratio is one oxygenation marker. Ventilator settings, PEEP, SpO₂, ABG timing and diagnosis matter.
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Model how the ratio changes if PaO₂ or FiO₂ changes, without overwriting your main result.
Calculate your baseline first
The PF ratio is PaO₂ ÷ FiO₂, where PaO₂ is arterial oxygen pressure in mmHg and FiO₂ is inspired oxygen as a decimal fraction. For example, PaO₂ 90 mmHg on FiO₂ 0.21 gives a PF ratio around 429.
This tool highlights common oxygenation bands: 400+ normal, 300–399 adequate, 200–299 mild impairment, 100–199 moderate impairment and <100 severe impairment.
No. PF ratio contributes to ARDS severity assessment, but diagnosis also depends on timing, imaging, origin of edema, PEEP/CPAP level and clinical judgement. Use this calculator as a math aid, not a diagnosis.
Results are estimates generated locally in your browser using the formula PaO₂ ÷ FiO₂. This tool is for informational and educational purposes only, not medical advice, diagnosis, triage or treatment guidance. Interpret ABG and oxygenation results with qualified clinical professionals. VisionVix accepts no liability for decisions based on this output.
