Total Lung Capacity: How Much Air Can Your Lungs Hold?

The average adult total lung capacity (TLC) is 5–6 liters (≈200–240 oz). It is the sum of four lung volumes:

• Tidal Volume (TV): ~500 mL – air moved in/out during quiet breathing.
• Inspiratory Reserve Volume (IRV): ~3000 mL – additional air inhaled maximally after normal inspiration.
• Expiratory Reserve Volume (ERV): ~1200 mL – additional air exhaled forcefully after normal expiration.
• Residual Volume (RV): ~1200 mL – air remaining after maximal exhalation; cannot be measured by spirometry.

TLC = TV + IRV + ERV + RV

Influencing Factors

• Age, sex, height, fitness, altitude, posture, lung disease (COPD ↑ TLC, restriction ↓ TLC).

Clinical Measurement

• Body plethysmography (gold standard for TLC/RV).
• Helium dilution, nitrogen washout.
• Spirometry measures VC, FVC, FEV₁ – not RV or TLC directly.

Lung volumes are key in diagnosing obstructive vs. restrictive lung disease.