Lung Capacity Estimator
Estimate predicted lung capacity (FVC) from age, height, and sex using the Knudson equations.
Enter a spirometry result to see your percent of predicted.
Lung capacity (FVC) estimation predicts your Forced Vital Capacity, the maximum volume of air you can push out in a single hard breath, from age, height, and sex using standard spirometry reference equations.
Predicted FVC formulas (Knudson equations, long used in clinical practice):
Males: FVC (liters) = (0.0576 × Height in cm) − (0.0269 × Age) − 4.34
Females: FVC (liters) = (0.0443 × Height in cm) − (0.0261 × Age) − 2.89
Height carries most of the weight in both, which is why a tall 60-year-old often has a larger FVC than a short 25-year-old. Age subtracts about 27 mL a year in men and 26 mL in women, so roughly a quarter of a liter per decade.
Important note: reference equations differ by population, and this matters more than people expect. The Global Lung Initiative (GLI-2012) equations are the current international standard and are what a hospital lab will use. They include population-specific coefficients that Knudson does not, so the figure below can differ from a clinic report by several percent. Use it to understand the shape of the relationship, not to second-guess a spirometry result.
Predicted FVC by age and height, from the formulas above:
| Age | Men, 165 cm | Men, 175 cm | Men, 185 cm | Women, 155 cm | Women, 165 cm | Women, 175 cm |
|---|---|---|---|---|---|---|
| 25 | 4.49 L | 5.07 L | 5.64 L | 3.32 L | 3.77 L | 4.21 L |
| 40 | 4.09 L | 4.66 L | 5.24 L | 2.93 L | 3.38 L | 3.82 L |
| 55 | 3.68 L | 4.26 L | 4.84 L | 2.54 L | 2.98 L | 3.43 L |
| 70 | 3.28 L | 3.86 L | 4.43 L | 2.15 L | 2.59 L | 3.04 L |
Lung function interpretation (% of predicted FVC). This is the number a doctor actually reads, and it needs a measured spirometry result as well as a predicted one. Enter yours below and the calculator will work it out.
| % Predicted | Interpretation |
|---|---|
| 100%+ | Above the predicted value, which is common in trained people |
| 80-99% | Normal range |
| 70-79% | Mild reduction |
| 60-69% | Moderate reduction |
| Below 60% | Severe reduction, worth a medical review |
A low FVC on its own does not say why. Spirometry separates the two main patterns using the FEV1/FVC ratio: obstruction, as in asthma or COPD, empties slowly so the ratio falls below about 0.7, while restriction, as in fibrosis or obesity, holds less air but empties normally so the ratio stays normal or rises. This calculator does not estimate FEV1, so it cannot tell you which you have.
Worked example: Male, 42 years old, 178 cm tall. FVC = (0.0576 × 178) − (0.0269 × 42) − 4.34 FVC = 10.25 − 1.13 − 4.34 = 4.78 liters predicted
If spirometry measures 3.8 L: 3.8 ÷ 4.78 = 79.5% of predicted, a mild reduction.
Factors that reduce FVC: smoking, obesity, scoliosis, neuromuscular disease, pulmonary fibrosis. Factors that increase it: endurance training, swimming in particular, tall stature, and being young. Aerobic exercise does not stop the age-related decline, but it does start you from a higher point and slows the slope, which over thirty years adds up to a great deal.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.