Predicted Vital Capacity (VC) Calculator

Vital capacity is the maximum volume of air that can be exhaled after a maximal inhalation. Physiologically, VC is the sum of three lung volumes: tidal volume (TV) + inspiratory reserve volume (IRV) + expiratory reserve volume (ERV). Typical values for healthy adults range from 3–5 liters — larger in men and taller people.

VC (slow vital capacity) is measured with a maximal exhalation without a speed requirement; FVC (forced vital capacity) is measured with an exhalation as fast and forceful as possible; TLC (total lung capacity) is all the air in the lungs, i.e. VC + residual volume (RV). In healthy people, FVC is almost equal to VC. RV cannot be measured with ordinary spirometry, so TLC requires additional equipment such as body plethysmography.

Enter sex, age, and height, then choose a reference equation. The calculator computes the predicted value — for example, a 175 cm/40-year-old man ≈ 4.05 L per Baldwin 1948, 4.70 L per ECSC 1993, and 5.11 L per NHANES III. If you have spirometry results, enter the measured value to see % predicted and the lower limit of normal (LLN).

% predicted = (measured value ÷ predicted value) × 100%. It shows where your result stands relative to the average of healthy people your age and height. LLN (lower limit of normal) is the lower limit of normal — statistically equivalent to the 5th percentile of the healthy population — so a value below the LLN is considered abnormal even if the % predicted still looks decent.

As an educational guide following ATS/ERS convention: ≥80% normal; 60–79% mild reduction; 40–59% moderate reduction; <40% severe reduction. This is a simplification — the current 2022 ATS/ERS guidelines use z-scores, not % predicted. Valid clinical interpretation still requires quality spirometry and a doctor’s assessment.

Height is the biggest determinant, followed by age (VC declines about 20–30 mL per year), sex, and ethnicity. Beyond that: posture during measurement (standing slightly larger than sitting), smoking, lung diseases such as asthma/COPD/fibrosis, severe obesity, pregnancy, and high-altitude acclimatization. Reference equations only adjust for height, age, sex, and ethnicity.

Because they were derived from different populations and eras: Baldwin 1948 from a 1940s general population (slow VC); ECSC 1993 a compilation of European data (range 18–70 years); NHANES III 1999 a United States population survey with three ethnic groups and modern spirometry technique. Differences of 0.3–0.6 L between equations are common and reflect the diversity of the reference populations.

Generally to monitor chronic lung disease, assess treatment response, pre-operative evaluation, or periodic checkups for at-risk workers. The repeat interval is set by the doctor based on the condition — for example 3–12 months in chronic disease. The Serial Trend mode in this calculator helps log results over time to discuss with your doctor.

Aerobic exercise and respiratory muscle training can improve breathing efficiency and slightly increase the volume of air that can be mobilized, but VC is largely determined by ribcage size (anatomy). Product claims promising large VC gains in a short time should be viewed skeptically.

No. This is an educational tool: it calculates predicted numbers from the data you enter, but it does not assess spirometry maneuver quality, does not know your symptoms, and does not establish a diagnosis. Results far below predicted — or any respiratory symptoms — should be brought to a doctor or spirometry facility.

With a spirometer meeting ATS/ERS standards, performed by trained personnel: sit upright (or stand per protocol), nose clipped, maximal inhalation, then exhale maximally until no more air comes out. The maneuver is repeated at least three times and the largest reproducible value is taken. This calculator cannot verify your maneuver quality.

VC assesses lung volume size (restrictive pattern when VC is reduced with a normal ratio), while the FEV1/FVC ratio assesses airflow obstruction (obstructive pattern when below 70%). The two complement each other in spirometry interpretation. See also our FEV1/FVC ratio calculator to assess the obstructive component.