# Tidal Volume Calculator

Calculate ideal tidal volume for mechanical ventilation using the Devine ideal body weight formula. Supports ARDSNet lung-protective ventilation targets.

## What this calculates

Tidal volume for mechanical ventilation should be based on ideal body weight, not actual body weight. This calculator uses the Devine formula to estimate ideal body weight from height and sex, then calculates the tidal volume at your target mL/kg setting.

## Inputs

- **Sex** — options: Male, Female
- **Height** (cm) — min 100, max 250
- **Target Tidal Volume** (mL/kg IBW) — min 4, max 10 — ARDSNet recommends 6 mL/kg IBW for lung-protective ventilation. General range: 6-8 mL/kg.

## Outputs

- **Ideal Body Weight (IBW)** — Predicted body weight using the Devine formula
- **Tidal Volume** — Calculated tidal volume at your target mL/kg
- **Lung-Protective Range (6-8 mL/kg)** — formatted as text — Tidal volume range at 6 and 8 mL/kg IBW
- **ARDSNet Target (6 mL/kg)** — Tidal volume at the ARDSNet-recommended 6 mL/kg IBW

## Details

The ARDSNet trial demonstrated that lower tidal volumes (6 mL/kg of ideal body weight) reduce mortality in patients with acute respiratory distress syndrome compared to traditional volumes of 12 mL/kg. Today, lung-protective ventilation using 6 to 8 mL/kg of IBW is standard practice for most mechanically ventilated patients, not just those with ARDS.

Ideal body weight is calculated using the Devine formula: for males, IBW = 50 + 2.3 x (height in inches - 60); for females, IBW = 45.5 + 2.3 x (height in inches - 60). This formula was originally designed for drug dosing but has become the standard for ventilator settings because lung size correlates more closely with height than with actual body weight.

Using actual body weight for tidal volume calculations in obese patients leads to overdistension and ventilator-induced lung injury. A 5'4" woman has the same lung capacity regardless of whether she weighs 130 or 250 pounds, so her tidal volume should be the same. Always use predicted or ideal body weight for ventilator settings.

## Frequently Asked Questions

**Q: Why use ideal body weight instead of actual weight?**

A: Lung size is determined by height and sex, not by how much a person weighs. An obese patient's lungs are not larger than those of a normal-weight person of the same height. Using actual weight in overweight patients leads to excessively large tidal volumes, which can cause ventilator-induced lung injury through overdistension of the alveoli.

**Q: What tidal volume should I target?**

A: For most mechanically ventilated patients, 6 to 8 mL/kg of ideal body weight is the accepted range. Patients with ARDS should be ventilated at the lower end (6 mL/kg) per the ARDSNet protocol. Higher volumes (up to 8 mL/kg) may be appropriate for patients without lung injury, but many intensivists now default to 6 mL/kg for everyone.

**Q: What if the calculated IBW seems too low?**

A: The Devine formula can produce very low or even negative values for very short patients (under about 5 feet). In those cases, clinical judgment is essential. Some clinicians use adjusted body weight or simply set the tidal volume based on plateau pressures and clinical response rather than strictly following the formula.

**Q: Does this replace clinical judgment?**

A: No. This calculator is a starting point for ventilator settings. Actual tidal volume should be titrated based on plateau pressures (target below 30 cm H2O), blood gas results, patient comfort, and clinical response. Ventilator management is complex and must be guided by trained clinicians.

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Source: https://vastcalc.com/calculators/health/tidal-volume
Category: Health & Fitness
Last updated: 2026-04-08