Calculator

SpO₂/FiO₂ ratio

New

Non-invasive oxygenation ratio; valid only when SpO₂ ≤ 97%. Global ARDS definition uses S/F ≤ 315.

%
fraction 0.21-1.0

S/F ratio

230

Consistent with ARDS oxygenation criterion (≤ 315)

Consistent with ARDS oxygenation criterion (≤ 315)
Above ARDS threshold

Formula

spo2 / fio2

References

  1. Matthay MA, et al. A new global definition of acute respiratory distress syndrome. Am J Respir Crit Care Med 2024;209:37-47.

Used in

Oxygen prescription and SpO2 targetsHigh-flow nasal oxygen and the ROX indexDefining and diagnosing ARDSPaediatric airway: sizes, RSI and first ventilator settingsBronchiolitis and croup

Calculators support, not replace, clinical judgement. Check inputs and units, and confirm doses with your unit protocol.