Why is tidal volume based on ideal body weight, not actual weight?

Lung size correlates with height and sex, not actual body weight. In obese patients, using actual weight would deliver dangerously large tidal volumes, causing ventilator-induced lung injury (VILI). IBW keeps the delivered volume proportional to functional lung capacity.

What is the ARDSNet tidal volume target?

The landmark ARDSNet trial (NEJM 2000) showed that ventilating with 6 mL/kg IBW reduced mortality compared to 12 mL/kg IBW. Current guidelines recommend 6–8 mL/kg IBW for ARDS, and 6–8 mL/kg IBW is increasingly used as a default lung-protective strategy in all mechanically ventilated patients.

What IBW formula does this calculator use?

The ARDSNet protocol defines IBW as: Males: 50 + 2.3 × (height in inches − 60); Females: 45.5 + 2.3 × (height in inches − 60). This is the Devine formula, the same one used in the original ARDSNet trial.

What if the calculated IBW is very low?

For very short patients the IBW can be low, sometimes yielding a minimum VT that makes adequate ventilation difficult. In practice, a minimum tidal volume of about 200–250 mL is used as a floor. Clinician judgment and plateau pressure monitoring remain essential.

Should I always use 6 mL/kg IBW?

6 mL/kg IBW is the standard starting point for ARDS. For patients with normal lungs, 6–8 mL/kg IBW is safe. The key targets alongside VT are plateau pressure ≤30 cmH₂O and driving pressure ≤15 cmH₂O. Always titrate based on the individual patient response.

Tidal Volume Calculator

Name: Tidal Volume Calculator
Availability: InStock
Author: Nham Vu

Enter patient sex and height to get ideal body weight and ARDSNet lung-protective tidal volume (6 mL/kg IBW) for mechanical ventilation.

Patient Parameters

Biological Sex

Male Female

Height

Use actual measured height; do not estimate from patient report if possible.

Ideal Body Weight (IBW)

—

kg (Devine formula)

Target Tidal Volume (6 mL/kg IBW)

—

ARDSNet VT Range (6–8 mL/kg IBW)

IBW	6 mL/kg	8 mL/kg
40 kg	240 mL	320 mL
50 kg	300 mL	400 mL
60 kg	360 mL	480 mL
70 kg	420 mL	560 mL
80 kg	480 mL	640 mL
90 kg	540 mL	720 mL

Summary

Enter patient sex and height to get ideal body weight and ARDSNet lung-protective tidal volume (6 mL/kg IBW) for mechanical ventilation.

How it works

Select the patient's biological sex (male or female).
Enter the patient's height in centimeters or inches.
The calculator derives ideal body weight (IBW) using the ARDSNet formula.
Target tidal volume is computed as IBW × 6 mL/kg (ARDSNet lower bound).
The safe range of 6–8 mL/kg IBW is displayed alongside the calculated IBW.
Use the result to set initial ventilator tidal volume for lung-protective strategy.

Use cases

Set initial tidal volume when intubating an ARDS or ALI patient.
Quickly verify ventilator VT settings at the bedside in the ICU.
Teach ARDSNet lung-protective ventilation principles to residents.
Cross-check VT when transferring a ventilated patient between units.
Apply lung-protective settings prophylactically in at-risk surgical patients.
Screen for over- or under-ventilation relative to the 6 mL/kg IBW target.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu