IBW / Tidal Volume Calculator
Calculate ideal body weight and lung-protective tidal volume ranges. Respiratory therapists use predicted body weight, not actual body weight, when choosing initial ventilator tidal volume targets.
Calculate IBW and Tidal Volume Range
Enter sex and height. The calculator estimates IBW and tidal volumes at 4, 6, and 8 mL/kg.
IBW / Predicted Body Weight Formula
Female: PBW = 45.5 + 2.3(height in inches − 60)
Tidal Volume = PBW × mL/kg target
Ventilator VT Is Based on Height, Not Weight
For lung-protective ventilation, tidal volume is based on predicted body weight because lung size is more closely related to height than actual body weight.
The lungs do not get bigger just because the patient weighs more. Use predicted body weight for VT settings.
Common Tidal Volume Targets
| Target | Meaning | Common Use |
|---|---|---|
| 4 mL/kg | Very low VT target | Severe lung-protective strategies when clinically appropriate. |
| 6 mL/kg | Lung-protective VT target | Common target in ARDS/lung-protective ventilation. |
| 8 mL/kg | Upper lung-protective range | Often used as an upper reference in non-ARDS contexts depending on patient and strategy. |
Example Calculation
PBW = 45.5 + 2.3(64 − 60)
PBW = 45.5 + 9.2 = 54.7 kg
6 mL/kg VT = 54.7 × 6 = 328 mL
Lung-Protective Ventilation Reduces Overdistension
Using excessive tidal volume can contribute to volutrauma and ventilator-induced lung injury. Lung-protective ventilation uses smaller tidal volumes based on predicted body weight to reduce overdistension risk.
Can overdistend alveoli and worsen lung injury.
May increase PaCO₂ depending on rate, dead space, and patient condition.
VT is only one setting. Always connect it to pH, PaCO₂, plateau pressure, oxygenation, and patient goals.
When ARDS is present, think lower VT and monitor plateau pressure.
Avoid These Errors
Ventilator VT targets should use predicted body weight, not actual weight.
The common PBW formula uses height in inches.
Calculate a range so you can understand 4, 6, and 8 mL/kg targets.
VT must be connected to plateau pressure and lung mechanics.
Connect Tidal Volume to Ventilator Mechanics
After choosing a VT target, evaluate plateau pressure, compliance, resistance, CO₂ clearance, and oxygenation.