# RSBI Calculator (Rapid Shallow Breathing Index)

URL: https://speedycalculator.com/calculators/health/rsbi/
Last updated: 2026-10-30

> The RSBI calculator divides respiratory rate by tidal volume in litres during a spontaneous breathing trial to predict whether a patient is likely to be weaned successfully from the ventilator.

## Inputs

- Respiratory rate (breaths/min)
- Tidal volume (mL, L, fl oz)

## Results

- RSBI

## Formula

```
RSBI = respiratory rate (breaths/min) ÷ tidal volume (L)
< 105: weaning likely to succeed · ≥ 105: likely to fail
```

## Explanation

Patients who cannot breathe on their own tend to breathe fast and shallow. Yang and Tobin showed in 1991 that an RSBI below 105 predicted successful extubation. It is one part of a broader weaning assessment.

### How to use the RSBI Calculator

- **Respiratory rate**
- **Tidal volume**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Measure respiratory rate and average tidal volume over about one minute of spontaneous breathing.

### Inputs explained

FieldWhat to enterRespiratory rateIn breaths/minTidal volumeUnits: mL, L, fl oz

### Example values

How the main result changes when **Respiratory rate** changes and everything else stays at the example values above:

Respiratory rate (breaths/min)RSBI (breaths/min/L)112816.541225527.569338344110
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Respiratory rate: 22 breaths/min; Tidal volume: 400 mL.

Results — **RSBI = 55 breaths/min/L**.

## Key terms

- **RSBI**: Rapid shallow breathing index (f/VT).

## FAQ

**What is a good RSBI?**
Below 105; many units also look for values below 80.

**Is RSBI enough to decide extubation?**
No – mental status, secretions, cough and oxygenation also matter.

**When should RSBI be measured?**
During a spontaneous breathing trial on minimal support.


## Sources

- [Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med, 1991](https://pubmed.ncbi.nlm.nih.gov/2032573/)