Calculator Inputs
Example Data Table
| Profile | Sex | Age | Height | Weight | Rate | Estimated VC | Estimated TLC |
|---|---|---|---|---|---|---|---|
| Office Engineer | Male | 32 | 178 cm | 74 kg | 14/min | 5.11 L | 6.34 L |
| Field Technician | Female | 29 | 165 cm | 60 kg | 15/min | 3.55 L | 4.55 L |
| Endurance Athlete | Male | 27 | 182 cm | 78 kg | 16/min | 5.81 L | 7.20 L |
Formula Used
1) Predicted Forced Vital Capacity
Male: FVC = (0.052 × height in cm) − (0.022 × age) − 3.60
Female: FVC = (0.041 × height in cm) − (0.018 × age) − 2.69
2) Predicted FEV1
Male: FEV1 = (0.0414 × height in cm) − (0.0244 × age) − 2.190
Female: FEV1 = (0.0342 × height in cm) − (0.0255 × age) − 1.578
3) Adjustment Layer
Adjusted Capacity = Predicted Value × posture factor × profile factor × smoking factor
4) Volume Components
Tidal Volume = 7 mL × body weight in kg × activity factor
Vital Capacity = Tidal Volume + Inspiratory Reserve + Expiratory Reserve
Functional Residual Capacity = Expiratory Reserve + Residual Volume
Total Lung Capacity = Vital Capacity + Residual Volume
5) Ventilation Metrics
Minute Ventilation = Tidal Volume × Respiratory Rate
Alveolar Ventilation = (Tidal Volume − Dead Space) × Respiratory Rate
Air Exchange Efficiency = Alveolar Ventilation ÷ Minute Ventilation × 100
How to Use This Calculator
- Choose metric or imperial units first so your height and weight match the expected format.
- Enter age, biological sex, height, weight, respiratory rate, and dead space volume.
- Select posture, activity level, respiratory profile, and smoking history for a more detailed adjustment.
- Press Calculate Lung Capacity to show results above the form.
- Review the result cards, table summary, and Plotly graph for volume distribution.
- Use the CSV or PDF buttons to export the current report.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates vital capacity, total lung capacity, FEV1, reserve volumes, and ventilation metrics using body size, breathing inputs, and adjustment factors.
2) Is this the same as a hospital spirometry test?
No. This is an engineering-style estimation tool. It helps with planning and learning, but it does not replace measured spirometry or clinical review.
3) Why does posture affect the result?
Posture can slightly influence chest expansion and diaphragm movement. Standing often supports larger volumes than sitting or lying flat.
4) Why include dead space volume?
Dead space helps estimate alveolar ventilation. It separates total moved air from the portion actually available for gas exchange.
5) What is the difference between VC and TLC?
Vital capacity is the movable portion of lung air. Total lung capacity also includes residual volume that remains after maximum exhalation.
6) Can athletes show higher values?
Yes. Athletic conditioning can improve breathing efficiency and sometimes increase usable capacity, so this calculator includes an athlete adjustment profile.
7) Does smoking history change the estimate?
Yes. The model applies a reduction factor for former and current smoking history to reflect lower expected performance.
8) When should I use the export buttons?
Use them after calculation when you want a saved report, shared estimate sheet, or a printed summary for project notes or study records.