# Lung Capacity Calculator

Uses lung volumes to determine vital, inspiratory and functional residual capacity.

In the text below the form you can find the formulas used and more information about factors that affect lung capacity.

The lung capacity calculator determines all the respiratory capacities:

■ Vital capacity (VC);

■ Inspiratory capacity (IC);

■ Functional residual capacity (FRC);

■ Total lung capacity (TLC).

based on inspiratory, tidal, expiratory reserve and residual volume that have been measured through spirometry.

The following table introduces the four equations used in the calculator and the normal expected values for the respiratory capacities, differentiated by gender:

 Lung capacity Formula Men (L) Women (L) Vital capacity (VC) IRV + TV + ERV 4.6 3.1 Inspiratory capacity (IC) IRV + TV 3.5 2.4 Functional residual capacity (FRC) ERV + RV 2.3 1.8 Total lung capacity (TLC) IRV + TV + ERV + RV 5.8 4.2

Inspiratory reserve volume
Tidal volume
Expiratory reserve volume
Residual 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

There are four respiratory volumes (determined by spirometry) required to indirectly calculate the respiratory capacity:

 Respiratory volume Symbol Normal Description Inspiratory reserve volume IRV 3 L The amount of air that can be forcefully inspired after a normal inspiration. Tidal volume TV 0.5 L The volume of air which is circulated through inhalation and expiration during one normal respiration. Expiratory reserve volume ERV 1.2 L The volume of air which can be exhaled forcefully after a normal expiration. Residual volume RV 1.2 L The amount of air that remains in the lungs after normal expiration.

The four lung capacities are calculated as follows:

Vital capacity (VC) = Inspiratory reserve volume (IRV) + Tidal volume (TV) + Expiratory reserve volume (ERV)

Inspiratory capacity (IC) = Inspiratory reserve volume (IRV) + Tidal volume (TV)

Functional residual capacity (FRC) = Expiratory reserve volume (ERV) + Residual volume (RV)

Total lung capacity (TLC) = Inspiratory reserve volume (IRV) + Tidal volume (TV) + Expiratory reserve volume (ERV) + Residual volume (RV)

The following table summarizes the above formulas and introduces the normal values for the four pulmonary capacities, differentiated by gender:

 Lung capacity Formula Men (L) Women (L) Vital capacity (VC) IRV + TV + ERV 4.6 3.1 Inspiratory capacity (IC) IRV + TV 3.5 2.4 Functional residual capacity (FRC) ERV + RV 2.3 1.8 Total lung capacity (TLC) IRV + TV + ERV + RV 5.8 4.2

## Lung capacity variations

Lung capacity can be defined as the maximum amount of air that can be breath in. There are physiological and pathological factors that impact on LC.

The first physiological factor is age, followed by diet and weight. A diet rich in vitamins, especially E and C can help support respiratory function whilst a diet high in fats will impact it. Obese and sedentary people tend to have less lung capacity.

LC is also affected during pregnancy because of the pressure of the diaphragm on the lungs. This is when functional residual capacity temporarily drops by almost 20%. However, the tidal volume increases to support the ventilation requirement. Professional athletes will have a higher lung capacity.

Restrictive pulmonary diseases, such as pulmonary fibrosis or pneumothorax, decrease lung volumes therefore decrease pulmonary capacity.

Pathological increases in lung volumes are observed in obstructive pulmonary diseases, such as asthma or chronic obstructive pulmonary disease.

## References

1. Flesch JD, Dine CJ. Lung volumes: measurement, clinical use, and coding. Chest. 2012; 142(2):506-10.

2. Ruppel GL. What is the clinical value of lung volumes? Respir Care. 2012; 57(1):26-35.

3. Jones RL, Nzekwu MM. The effects of body mass index on lung volumes. Chest. 2006; 130(3):827-33.

Specialty: Pulmonology

System: Respiratory

Objective: Determination

Type: Calculator

No. Of Variables: 4

Article By: Denise Nedea

Published On: June 13, 2017

Last Checked: June 13, 2017

Next Review: June 13, 2023