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Tidal Volume Calculator — Lung-Protective Ventilation by Predicted Body Weight

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.

Sex

Height unit

Height

Target tidal volume

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How it works

Predicted body weight (kg): men = 50 + 0.91 × (height cm − 152.4); women = 45.5 + 0.91 × (height cm − 152.4). Tidal volume = PBW × target mL/kg (ARDSNet: start at 8, reduce to 6 mL/kg; range 4–8). 1 in = 2.54 cm.

Lung size depends on height and sex, not on actual body weight, so protective ventilation is dosed on predicted body weight. The ARDS Network trial (NEJM 2000) showed that 6 mL/kg PBW with a plateau pressure of 30 cmH₂O or less reduced mortality from 39.8% to 31.0% compared with 12 mL/kg. Low tidal volumes (6–8 mL/kg PBW) are now also recommended for most mechanically ventilated patients without ARDS.

Worked example

For a man 175 cm tall: PBW = 50 + 0.91 × (175 − 152.4) = 50 + 20.6 = 70.6 kg. At 6 mL/kg the target tidal volume is 70.6 × 6 = 423 mL, within a 4–8 mL/kg range of 282–565 mL.

Sources: ARDS Network — Ventilation with lower tidal volumes (NEJM 2000) · ARDSNet — NIH NHLBI ventilator protocol card

Frequently asked questions

Why use predicted rather than actual body weight?

Lungs do not grow with fat mass. Dosing on actual weight in an obese patient would give an injuriously large tidal volume; predicted body weight from height and sex matches lung size.

What tidal volume is lung-protective?

6 mL/kg of predicted body weight is the ARDSNet target, adjusted between 4 and 8 mL/kg to keep plateau pressure at or below 30 cmH₂O and driving pressure ideally below 15 cmH₂O.

Is this the same as ideal body weight?

The ARDSNet predicted body weight is essentially the Devine ideal body weight formula (50 or 45.5 kg + 2.3 kg per inch over 5 feet) written in centimetres.

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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.