# What is the tidal volume by height?

Works out predicted body weight from height and sex with the ARDS Network formula, and the tidal volume at a chosen mL per kg of predicted body weight, with the 4 to 8 mL/kg range.

- Page: https://www.acalculator.org/health/tidal-volume-calculator
- JSON spec: https://www.acalculator.org/health/tidal-volume-calculator.json
- Version: d435bd2bdbac

## Default answer

Example with the default inputs (Sex Male, Height 5 ft 10 in, Tidal volume (mL/kg) 6): At 6 mL/kg, a predicted body weight of 73.1 kg gives a tidal volume of 439 mL.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| sex | Sex | Sex, which sets the formula: 50 kg (male) or 45.5 kg (female) at 152.4 cm. |
| height | Height | Height, from 124 cm (4 ft 0.8 in) to 250 cm. |
| mlkg | Tidal volume (mL/kg) | Millilitres per kg of predicted body weight, from 4 to 8. The ARDS Network trial started at 6. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| tidal | Tidal volume | mL per kg × predicted body weight, to the nearest mL. |
| pbw | Predicted body weight (kg) | 50 (male) or 45.5 (female) + 0.91 × (height in cm − 152.4), to 1 decimal. |
| low | At 4 mL/kg | The low end of the 4 to 8 mL/kg range, to the nearest mL. |
| high | At 8 mL/kg | The high end of the 4 to 8 mL/kg range, to the nearest mL. |

## Method

PBW (kg) = 50 + 0.91 × (height cm − 152.4) for men, 45.5 + 0.91 × (height cm − 152.4) for women. Tidal volume (mL) = mL/kg × PBW.

## Assumptions

- Predicted body weight comes from height and sex only; actual weight is not used.
- The ARDS Network trial was in adults with acute lung injury or ARDS on a ventilator. The page shows the arithmetic; it does not set a ventilator.
- Values are worked from the exact typed height and rounded once: PBW to 1 decimal and volumes to the nearest mL, halves up.

## Worked examples

1. sex = male, height = 1.778, mlkg = 6 gives pbw = 73.114, tidal = 438.684, low = 292.456, high = 584.912. Source: ARDS Network 2000: PBW = 50 + 0.91 × (177.8 − 152.4) = 73.114 kg.
2. sex = female, height = 1.65, mlkg = 6 gives pbw = 56.966, tidal = 341.796. Source: ARDS Network 2000: PBW = 45.5 + 0.91 × (165 − 152.4) = 56.966 kg.
3. sex = male, height = 1.524, mlkg = 8 gives pbw = 50, tidal = 400, low = 200, high = 400. Source: ARDS Network 2000: PBW = 50 kg at 152.4 cm.
4. sex = female, height = 1.524, mlkg = 4 gives pbw = 45.5, tidal = 182. Source: ARDS Network 2000: PBW = 45.5 kg at 152.4 cm.
5. sex = male, height = 1.85, mlkg = 6.5 gives pbw = 79.666, tidal = 517.829.

## FAQ

### How is tidal volume worked out from height?

First the predicted body weight (PBW): 50 kg for men or 45.5 kg for women, plus 0.91 kg for each cm of height over 152.4 cm (5 ft). Then multiply by the mL per kg: at 6 mL/kg, a man 5 ft 10 in tall (PBW 73.1 kg) gets about 439 mL.

### Why use predicted body weight and not actual weight?

Lung size follows height and sex, not body fat. The ARDS Network trial set tidal volume by predicted body weight, so a heavy person does not get larger breaths than their lungs can hold.

### Why 6 mL/kg?

The ARDS Network trial (2000) started at 6 mL/kg of predicted body weight and found fewer deaths than with 12 mL/kg in people with acute lung injury and ARDS. The ARDS Network tools page gives tables for 4 to 8 mL/kg.

### Is the inch formula the same?

The ARDS Network site also gives 50 or 45.5 + 2.3 × (height in inches − 60). That is 0.9055 kg per cm, a little less than 0.91. This page uses the centimetre form of the 2000 paper, so results can differ by a few tenths of a kg.

### What heights does it accept?

124 cm to 250 cm. Martin and Richards (2017) note that the formulas are defined for heights above about 152 cm and become less valid below about 124 cm.

### Does the page set a ventilator?

No. It shows the arithmetic of the formula. Ventilator settings are a clinical decision.

## Sources

- Acute Respiratory Distress Syndrome Network. Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308. https://doi.org/10.1056/NEJM200005043421801 (retrieved 2026-10-05)
- NHLBI ARDS Network. Tools: predicted body weight formulas and tables. http://www.ardsnet.org/tools.shtml (retrieved 2026-10-05)
- Martin DC, Richards GN. Predicted body weight relationships for protective ventilation: unisex proposals from pre-term through to adult. BMC Pulm Med. 2017;17:85. https://doi.org/10.1186/s12890-017-0427-1 (retrieved 2026-10-05)