# Vital Capacity Calculator

Estimates the pulmonary VC based on tidal, inspiratory and expiratory reserve volumes.

Vital capacity is defined as the maximum amount of air possible to be expelled after a maximum inhalation.

It is being calculated based on three respiratory volumes: tidal, inspiratory and expiratory reserve volumes.

Vital capacity = Inspiratory reserve volume + Tidal volume + Expiratory reserve volume

The following table introduces the normal values for all volumes involved in the calculation:

 Lung volume Males (L) Females (L) Inspiratory reserve volume (IRV) 3.1 1.9 Tidal volume (TV) 0.5 0.5 Expiratory reserve volume (ERV) 1.2 0.7

Inspiratory reserve volume
Tidal volume
Expiratory reserve volume
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Steps on how to print your input & results:

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.

## Variables and formula

Vital capacity is an indicator of respiratory function that is based on three pulmonary volumes, which are measured via lung function tests (spirometry).

The three volumes are described in the table below:

 Lung volume Males (L) Females (L) Description Inspiratory reserve volume (IRV) 3.1 1.9 The additional air possible to be inhaled forcefully after the normal tidal volume inspired. Tidal volume (TV) 0.5 0.5 The amount of air which can be inhaled and exhaled during relaxed breathing at a rate of 12 to 20 breaths per minute. Expiratory reserve volume (ERV) 1.2 0.7 The additional air that can be extracted during forced exhalation, after the expiration of the normal tidal volume.

The formula used to estimate VC from the above is:

Vital capacity = Inspiratory reserve volume + Tidal volume + Expiratory reserve volume

In short: VC = IRV + TV + ERV

In the light of the above, vital capacity can be defined as the maximum amount of air possible to be expelled after a maximum inhalation.

Normal values in adults are between 3 and 5 litres and depend on gender, age, weight, height and ethnicity.

Taller individuals tend to have higher vital capacities (differences of 0.8L for every 6 in of height).

Also, there is a functional difference between VC levels during 20s and 30s and those at 50s.

Lower than normal values are suggestive of a restrictive lung disease (e.g. pulmonary fibrosis, pneumothorax).

Normal values don’t necessarily guarantee the absence of respiratory condition, for example in obstructive lung diseases (e.g. asthma, emphysema or chronic obstructive pulmonary disease), the VC may be normal or just slightly decreased.

## Another way to estimate VC

As part of the basic ventilator pulmonary function test, the spirometer record the lung volumes and other functional parameters such as the peak expiratory flow rate.

However, the VC can also be estimated, based on subject’s gender, age and height, via the following formulas:

Vital capacity for men (in litres) = ((27.63 –112 x Age in years) x Height in cm) / 1000

Vital capacity for women (in litres) = ((21.78 –101 x Age in years) x Height in cm) / 1000

## Why is vital capacity calculated?

The VC determination contributes to the following:

■ Diagnosing certain underlying lung diseases;

■ Determination of the severity of respiratory muscle impairment in neuromuscular disease;

■ Treatment decisions in the Guillain-Barre syndrome;

■ Treatment management of myasthenic crisis.

## References

1. Hutchinson J. On the capacity of the lungs, and on the respiratory functions, with a view of establishing a precise and easy method of detecting disease by the spirometer. Med Chir Trans. 1846; 29:137-252.

2. Godfrey MS, Jankowich MD. The Vital Capacity Is Vital: Epidemiology and Clinical Significance of the Restrictive Spirometry Pattern. Chest. 2016; 149(1):238-51.

Specialty: Pulmonology

System: Respiratory

Objective: Determination

No. Of Variables: 3

Article By: Denise Nedea

Published On: July 2, 2017

Last Checked: July 2, 2017

Next Review: July 2, 2023