Lung Capacity Calculator

Created by Małgorzata Koperska, MD
Reviewed by Bogna Szyk
Last updated: Feb 20, 2022

The lung capacity calculator helps you find the respiratory volumes of your or your patient's lungs.

Scroll down if you're not sure how to calculate Total Lung Capacity (TLC), vital capacity (VC), inspiratory capacity (IC), and functional residual volume (FRS).

The tool uses four lung volume measurements from spirometry, a ventilatory pulmonary function test:

  • IRV - Inspiratory Reserve Volume;
  • TV - Tidal Volume;
  • ERV - Expiratory Reserve Volume;
  • RV - Residual Volume.

How to calculate total lung capacity?

Total Lung Capacity (TLC) is the complete sum of the air volume in one's lungs. It can be calculated simply by adding up all the measured lung volumes:

TLC = IRV + TV + ERV + RV

The normal value range for adults is 5 to 7 liters. It depends on age, sex, height, mass, and ethnicity. You can read more on the normal values of lung capacities in this Statement of the European Respiratory Society.

How to calculate vital capacity?

Vital Capacity (VC) is the volume of air that can be expelled from the lungs after a maximal inhalation. The lung capacity calculator finds it by adding the Inspiratory Reserve Volume, Tidal Volume, and Expiratory Reserve Volume:

VC = IRV + TV + ERV

The normal value range for adults is 3 to 5 liters. The predicted value of this capacity can be estimated based on a patient's sex, age and height - use our vital capacity calculator to find it and compare the results.

💡 It is also possible to measure the Forced Vital Capacity (FVC). The doctors use this value to compute the FEV1/FVC ratio and estimate the level of obstruction or restriction of lungs.

How to calculate inspiratory capacity?

Inspiratory Capacity (IC) is the maximum volume of air that can be inhaled by the patient without a forced exhalation beforehand. The inspiratory capacity is calculated by adding the Inspiratory Reserve Volume and the Tidal Volume:

IC = IRV + TV

The normal range of inspiratory capacity is around 2 to 4 liters.

How to calculate functional residual capacity?

Functional Residual Capacity (FRS) is the volume of air that remains in our lungs during the whole process of normal breathing in a relaxed state, without forcing the exhalation. It's the sum of Expiratory Reserve Volume and Tidal Volume:

FRS = ERV + RV

A normal FRS should be around 2 liters.

The lung capacity calculator uses liters as default units, but you can switch between metric and imperial units. Click on the unit symbol and choose the unit you prefer.

Małgorzata Koperska, MD
Lung volumes
IRV - Inspiratory Reserve Volume
liters
TV - Tidal Volume
liters
ERV - Exspiratory Reserve Volume
liters
RV - Residual Volume
liters
Lung capacities
Total Lung Capacity
liters
Vital Capacity
liters
Functional Residual Capacity
liters
Inspiratory Capacity
liters
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