Free Lung Capacity Calculator
Enter IRV, TV, ERV, and RV to calculate your lung capacities
Understanding Lung Capacities with This Respiratory Volume Calculator
This lung capacity calculator serves as a comprehensive respiratory volume calculator, enabling you to derive key parameters from standard spirometry measurements. It functions as both a total lung capacity calculator and a vital capacity calculator, while also providing values for inspiratory capacity (IC) and functional residual capacity (FRC). All calculations are built upon four fundamental lung volumes:
- Inspiratory reserve volume (IRV)
- Tidal volume (TV)
- Expiratory reserve volume (ERV)
- Residual volume (RV)
These four volumes are typically obtained from a pulmonary function test (spirometry) and entered into the tool to compute the following capacities.
Total Lung Capacity (TLC)
TLC represents the total amount of air the lungs can contain after a maximal inhalation. It is determined by summing all four volumes:
In healthy adults, TLC normally falls between 5 and 7 liters. The exact figure depends on age, sex, height, weight, and ethnicity, as outlined by the European Respiratory Society.
Vital Capacity (VC)
Vital capacity is the maximum volume of air that can be expelled from the lungs following a deepest possible inspiration. The calculator computes it as:
A normal VC generally ranges from 3 to 5 liters. The tool can compare a measured VC with a predicted value derived from demographic data. (Forced vital capacity – FVC – is a related measurement used to calculate the FEV1/FVC ratio, which helps identify obstructive or restrictive breathing patterns. More details on that ratio can be found in a dedicated FEV1/FVC ratio tool.)
Inspiratory Capacity (IC)
Inspiratory capacity is the greatest volume that can be inhaled starting from the end of a normal expiration, without any forced exhalation beforehand. Its formula is:
Typical IC values range from 2 to 4 liters.
Functional Residual Capacity (FRC)
FRC refers to the amount of air remaining in the lungs after a relaxed, passive exhalation. It is the sum of the expiratory reserve volume and residual volume:
A normal FRC is approximately 2 liters.
Unit Options
The calculator uses liters as its default unit. If you prefer milliliters (mL), click the unit symbol next to any input field and select "mL" from the dropdown; all displayed volumes will update accordingly.
Important Note
This tool is designed for educational and informational purposes only. It should not replace a professional medical evaluation. If you have concerns about your respiratory health, please consult a physician.
FAQ
1. How can I calculate my total lung capacity (TLC)?
TLC is calculated by adding the inspiratory reserve volume (IRV), tidal volume (TV), expiratory reserve volume (ERV), and residual volume (RV): TLC = IRV + TV + ERV + RV. Enter these four volumes (obtained from spirometry) into the calculator to get your TLC.
2. What is the normal vital capacity range for adults?
Vital capacity (VC) normally lies between 3 and 5 liters in healthy adults. The calculator computes VC as IRV + TV + ERV and can also compare your measured value against a predicted norm based on age, sex, and height.
3. How do I switch the calculator from liters to milliliters?
Click the unit symbol (displayed as 'L') next to any input field and select 'mL' from the dropdown menu. The calculator will automatically convert all displayed volumes to milliliters.
4. What is the difference between inspiratory capacity (IC) and functional residual capacity (FRC)?
IC is the maximum volume you can inhale after a normal expiration (IC = IRV + TV; normal range 2–4 L). FRC is the volume left in your lungs after a relaxed exhalation (FRC = ERV + RV; around 2 L). They represent different phases of the breathing cycle.
How to Use
- Enter your Inspiratory Reserve Volume (IRV), Tidal Volume (TV), Expiratory Reserve Volume (ERV), and Residual Volume (RV) in milliliters or liters.
- Select the appropriate unit (mL or L) for each lung volume measurement.
- View your calculated Total Lung Capacity, Vital Capacity, Inspiratory Capacity, and Functional Residual Capacity instantly.