Calculate predicted total lung capacity, vital capacity, residual volume, and FRC by age, height, and sex. Visual breakdown of all lung volumes.
Total lung capacity (TLC) represents the maximum volume of air the lungs can hold after a full inspiration. It is the sum of all four lung volumes: tidal volume (VT), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), and residual volume (RV). Normal TLC in adults ranges from about 4 to 6 liters in women and 6 to 8 liters in men, with height being the strongest determinant.
Understanding predicted lung volumes is fundamental to pulmonary medicine. While spirometry measures dynamic volumes (FVC, FEV₁), static volumes like TLC, RV, and functional residual capacity (FRC) require body plethysmography or gas dilution techniques. These measurements are essential for distinguishing restrictive lung diseases (where TLC is reduced below 80% predicted) from obstructive diseases (where TLC may be normal or increased due to air trapping). The **RV/TLC ratio** is particularly important — values above 30% suggest air trapping commonly seen in COPD and emphysema.
Predicted values vary primarily by height, age, sex, and ethnicity. Height has the single largest effect, as longer torsos contain more alveoli. Age causes gradual decline in elastic recoil, increasing RV while maintaining or slightly decreasing TLC. Sex differences reflect average body size and chest wall dimensions. This calculator estimates all major lung volumes and capacities using established prediction equations, providing a visual breakdown helpful for understanding respiratory physiology.
Predicted lung volumes help show whether a patient is near the expected range for their body size or drifting into obstruction, restriction, or hyperinflation. This calculator keeps TLC, VC, RV, FRC, and RV/TLC together so the pattern is easier to read than a single number on its own.
Predicted values based on European Respiratory Society reference equations. Males: TLC = 7.99 × height(m) − 7.08; VC = 0.0576 × ht(cm) − 0.026 × age − 4.34; RV = 0.0216 × ht(cm) + 0.0207 × age − 2.84. FRC = ERV + RV. IC = TLC − FRC. VT ≈ 500 mL.
Result: TLC = 6.90 L
A 35-year-old male at 175 cm has a predicted TLC of ~6.90 L, vital capacity ~4.03 L, and residual volume ~1.35 L. The RV/TLC ratio of ~19.5% is well within normal limits.
Total lung capacity is only part of the story. A low TLC supports restriction, but an elevated RV or RV/TLC ratio can point toward air trapping and hyperinflation even when the total capacity looks less dramatic. That is why the full breakdown is more useful than TLC alone.
Predicted values vary with body size and demographics, so the same measured capacity can mean very different things in two patients. Comparing the measured volume against the predicted value helps decide whether the result is simply normal for body habitus or clinically abnormal.
VC, RV, FRC, and TLC each answer a different question about lung mechanics. Reading them together makes it easier to separate a purely restrictive pattern from obstruction with air trapping, especially when spirometry alone leaves the diagnosis uncertain.
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This worksheet estimates TLC, VC, RV, FRC, and IC from height-, age-, and sex-based prediction equations, then presents RV/TLC as a context check for air trapping. It is a reference-value worksheet, not a direct measurement, because measured static lung volumes still require plethysmography or gas dilution techniques.
Normal TLC varies widely: ~4–6 L for women and ~6–8 L for men. It depends primarily on height. TLC < 80% predicted suggests restrictive disease.
Residual volume is the air that remains in the lungs even after maximal exhalation — it cannot pass through the spirometer. Body plethysmography or gas dilution methods are needed.
RV/TLC > 30% suggests air trapping, commonly seen in COPD and emphysema. The patient cannot fully empty their lungs due to airway collapse during expiration.
Height is the strongest predictor of lung volumes. Taller individuals have larger thoracic cavities with more alveoli, resulting in proportionally larger TLC, VC, and other volumes.
Chronic smoking causes inflammation, loss of elastic recoil, and emphysematous destruction, which can increase TLC through hyperinflation while reducing vital capacity and raising residual volume. The overall pattern is more informative than any single lung volume by itself.
TLC is the total air the lungs can hold. Vital capacity (VC = TLC − RV) is the air you can actually move in and out. RV remains trapped and unavailable for ventilation.