π« Vital Capacity Calculator
What should your lungs hold?
Predicted vital capacity
For informational purposes only, not medical advice.
Predicted vital capacity comes from the Baldwin equations: for men, (27.63 minus 0.112 times age) times height in centimeters. A 40-year-old man who is 178 cm tall has a predicted VC of 4121 mL, about 4.1 liters. Spirometry results are read as percent of this predicted value, with 80 percent or more counting as normal.
Vital capacity is the biggest breath you can take, from full exhale to full inhale. It falls with age as the chest stiffens, rises with height, and runs lower in women, which is exactly what the equations encode.
How to Use This Calculator
Enter age, height, and sex for the predicted value, and optionally a measured spirometry result to get percent of predicted with an interpretation band.
Enter age in years, height in centimeters, and sex.
Read the predicted vital capacity in mL and liters.
Optionally enter a measured VC from spirometry to see percent of predicted and whether it falls in the normal range.
The Baldwin Equations
Published by Baldwin, Cournand, and Richards in 1948 from measurements on healthy subjects, these equations have survived three-quarters of a century because the relationships are genuinely linear: each year of age costs men about 0.112 mL per cm of height, each centimeter of height buys about 27 mL at young adulthood. Modern labs often use newer reference sets like the GLI equations, but Baldwin remains the classic bedside estimate.
Percent of predicted is the clinical currency: 80 percent or more is normal, 60 to 79 mild reduction, 40 to 59 moderate, under 40 severe. Those bands describe restriction; distinguishing restriction from obstruction needs the FEV1/FVC ratio alongside.
Worked Example
A 40-year-old man, 178 cm: 27.63 minus (0.112 times 40) equals 23.15; times 178 gives 4121 mL, or 4.12 liters. If his spirometry measured 3,800 mL, that is 92 percent of predicted, comfortably normal.
Now age him to 70 with the same height: 27.63 minus 7.84 equals 19.79, times 178 gives 3,523 mL. The same 3,800 mL measurement would then be 108 percent of predicted. Age changes the yardstick, which is why raw liters mislead and percent of predicted rules.
Reading Your Result
| Percent of predicted | Interpretation |
|---|---|
| 80% or more | Normal vital capacity. |
| 60 to 79% | Mild reduction. Correlate with symptoms and other indices. |
| 40 to 59% | Moderate reduction. Suggests significant restrictive or obstructive disease. |
| Under 40% | Severe reduction. Warrants full pulmonary evaluation. |
My take: a low VC alone never diagnoses. Restriction needs a low total lung capacity to confirm, and obstruction needs the FEV1/FVC ratio. Percent of predicted tells you something is off; the rest of the spirometry tells you what.
Limits
Baldwin's equations came from a mid-20th-century population and do not adjust for ethnicity, which modern GLI reference values do. Effort matters enormously: a half-hearted blow underestimates VC and fakes restriction. And predicted values are population averages; athletes and outliers legitimately exceed 100 percent.
Related Tools
Lung volumes meet exercise in the VO2 max calculator, body size in the BMI calculator, and activity dose in the MET minutes calculator.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is vital capacity?
The maximum air exhaled after a maximum inhalation, normally 3 to 5 liters in adults. It is the largest single breath the lungs can produce and a core spirometry measurement.
What is a normal vital capacity?
Roughly 80 percent or more of the predicted value for your age, height, and sex, typically 3 to 5 liters in adult men and 2 to 4 in women. Raw liters are meaningless without the predicted comparison.
How is predicted vital capacity calculated?
With reference equations like Baldwin's: (27.63 - 0.112 x age) x height in cm for men, (21.78 - 0.101 x age) x height for women. Modern labs may use GLI equations that add ethnicity adjustments.
What causes low vital capacity?
Restrictive lung disease (fibrosis), chest wall limitation (obesity, scoliosis), neuromuscular weakness, and poor effort. Obstructive diseases like COPD can also lower it through air trapping.
What is the difference between VC and FVC?
VC is measured with a slow exhalation; FVC (forced vital capacity) with a maximal fast blow. They are usually close; a much lower FVC suggests airway collapse during forced exhalation.
Can exercise increase vital capacity?
Training improves the muscles and efficiency of breathing more than the structural volume, though regular aerobic exercise can modestly raise measured VC. The predicted value itself is fixed by age, height, and sex.
Why does vital capacity fall with age?
Chest wall stiffening, weaker respiratory muscles, and loss of lung elasticity. The Baldwin equations build in about a 20-30 mL per year decline in typical adults.
Is 70% of predicted bad?
It indicates mild reduction and deserves context: symptoms, smoking history, and the rest of spirometry. Many people at 70 percent feel fine; the trend over time matters more than one reading.
Do the equations work for children?
No, pediatric reference values use different equations based on height primarily, since lung growth tracks height during development. This calculator is for adolescents and adults.
Who interprets spirometry results?
A clinician, usually a pulmonologist or primary care doctor, reading the full spirometry set with flow-volume loops. Percent of predicted is one piece; pattern recognition across indices makes the diagnosis.