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Total Lung Capacity Assessment

Enter patient demographics and measured TLC (plethysmography or helium dilution) to compute predicted TLC and percent predicted.

Results

Predicted TLC

6.50 L

Crapo et al. reference equations.

Percent predicted

94%

Total lung capacity within normal limits.

Interpretation:

  • <80% predicted: consistent with restriction (confirm with spirometry and DLCO).
  • 80–120% predicted: within normal limits.
  • >120% predicted: hyperinflation or measurement variability.

How to Use This Calculator

Use body plethysmography (preferred) or gas dilution. Ensure quality control according to ATS/ERS standards. Reference equations depend on sex, age, and height. Use standing height and chronological age. Combine TLC with spirometry, DLCO, and imaging to differentiate restrictive vs mixed patterns.

Formula

Male TLC (L) = 7.99 × height(m) − 0.007 × age − 7.17.

Reference: Crapo RO et al., Am Rev Respir Dis. 1981.

Frequently Asked Questions

Reference equations vary by population. Use laboratory-specific references when available; GLI equations include multi-ethnic references. Gas dilution may underestimate TLC in severe obstruction; plethysmography is preferred in COPD/emphysema. Consider imaging-based volume estimation (CT) or surrogate measures; interpret cautiously. Obesity may reduce TLC slightly. Correlate with restrictive spirometry and symptoms before labeling restriction. Repeat testing when symptoms change, after therapy, or annually in progressive diseases (e.g., ILD).