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ARDS Berlin Criteria Calculator — Mild, Moderate or Severe ARDS

Check the Berlin definition of acute respiratory distress syndrome (ARDS): timing, bilateral opacities, origin of oedema and PaO₂/FiO₂ on PEEP ≥ 5 cmH₂O — with the mild, moderate or severe grade and reported mortality.

PaO₂ unit
PaO₂
FiO₂
PEEP or CPAP
Onset within 1 week of a known insult or new/worsening respiratory symptoms
Bilateral opacities on chest X-ray or CT, not fully explained by effusions, collapse or nodules
Respiratory failure not fully explained by cardiac failure or fluid overload
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How it works

ARDS (Berlin 2012) requires all of: onset within 1 week; bilateral opacities; oedema not fully explained by cardiac failure or fluid overload; PaO₂/FiO₂ ≤ 300 mmHg on PEEP or CPAP ≥ 5 cmH₂O. Severity: mild 200 < P/F ≤ 300; moderate 100 < P/F ≤ 200; severe P/F ≤ 100. P/F = PaO₂ (mmHg) / FiO₂ (fraction); 1 kPa = 7.50062 mmHg.

The Berlin definition (ARDS Definition Task Force, JAMA 2012) replaced the 1994 American-European Consensus definition, dropping the term “acute lung injury” and requiring a minimum PEEP. In the validation cohort, hospital mortality rose from 27% (mild) to 32% (moderate) and 45% (severe). A 2023 global definition extends the criteria to high-flow oxygen and SpO₂/FiO₂, but Berlin remains the reference used in most trials.

Worked example

PaO₂ 75 mmHg on FiO₂ 50% gives P/F = 75 / 0.50 = 150 mmHg. With PEEP 8 cmH₂O, onset within a week, bilateral opacities and no cardiac explanation, all 5 criteria are met: moderate ARDS (100 < P/F ≤ 200), with 32% hospital mortality in the Berlin cohort.

Sources: ARDS Definition Task Force — The Berlin Definition (JAMA 2012)

Frequently asked questions

What P/F ratio is ARDS?

A PaO₂/FiO₂ of 300 mmHg or less on at least 5 cmH₂O of PEEP or CPAP, with the other Berlin criteria. 201–300 is mild, 101–200 moderate and 100 or less severe.

Why does PEEP have to be at least 5?

PEEP strongly affects oxygenation. Requiring a minimum of 5 cmH₂O standardises the conditions under which the ratio is measured; CPAP counts for mild ARDS when ventilation is non-invasive.

What happened to “acute lung injury”?

The Berlin definition removed it; the old ALI range (P/F 200–300) is now called mild ARDS.

Is there a newer ARDS definition?

A 2023 global definition adds patients on high-flow nasal oxygen and allows SpO₂/FiO₂ ≤ 315 when blood gases are not available. This calculator applies the Berlin 2012 criteria.

Related calculators

PaO₂/FiO₂ Ratio Calculator (P/F Ratio)
P/F ratio (PaO₂ ÷ FiO₂) in mmHg or kPa with Berlin and 2023 global ARDS oxygenation categories, the SpO₂/FiO₂ ratio and its cut-offs, the support needed for the criterion (ventilation, NIV/CPAP, high-flow oxygen), altitude-corrected P/F, the SOFA respiratory points and FiO₂ estimates for cannulas and masks.
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Calculate predicted (ideal) body weight from height and sex with the ARDSNet formula and the lung-protective tidal volume at 4–8 mL/kg — the 6 mL/kg target used in ARDS ventilation.
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Alveolar-arterial oxygen gradient from the alveolar gas equation — FiO₂, barometric pressure, PaCO₂, PaO₂ — with age-adjusted normal values to separate hypoventilation from V/Q mismatch, shunt and diffusion defects.
Oxygenation Index Calculator (OI & OSI)
Oxygenation index (FiO₂ × mean airway pressure ÷ PaO₂) and oxygen saturation index for ventilated patients — paediatric ARDS severity, ECMO thresholds and neonatal criteria.

Clinical decision tool for education and for use by trained clinicians alongside clinical judgement — not a diagnosis and not a substitute for medical assessment. Formulas and cut-offs come from the cited sources; local protocols may differ.