Vital Capacity Calculator
Use this vital capacity calculator to find your predicted forced vital capacity (FVC), lower limit of normal and percent predicted from age, sex and height.
Updated October 22, 2026
Medical Disclaimer: This calculator gives a general estimate for education only and cannot diagnose a condition. Share your result with your doctor or the clinician who ordered your test, and do not start, stop or change any medicine based on it. Read our full Medical Disclaimer.
How Vital Capacity Is Calculated
Vital capacity is the largest amount of air you can breathe out after filling your lungs as fully as you can. This calculator predicts the average forced vital capacity (FVC) for healthy people of your sex, age and height, shows the normal range around it, and compares your own FVC if you enter it.
What Vital Capacity Measures
Vital capacity shows how much air your lungs can move in one full breath. It is measured with spirometry, a breathing test where you blow into a tube connected to a machine. FVC is the volume blown out "as forcefully and completely as possible starting from full inspiration"⁴. A slow vital capacity, blown out at a relaxed pace, also exists, but FVC is the figure on almost every spirometry report and the one this calculator predicts. One number cannot show why it is high or low.
The Formula
Predicted FVC (M) = exp(a0 + a1 x ln(height) + a2 x ln(age) + Mspline)
Spread (S) = exp(p0 + p1 x ln(age) + Sspline)
Lower limit of normal (LLN) = M x (1 - 1.645 x L x S)^(1 / L)
z-score = ((measured FVC / M)^L - 1) / (L x S)
Percent predicted = measured FVC / M x 100
Males: a0 = -12.629131, a1 = 2.727421, a2 = 0.009174, p0 = -2.195595, p1 = 0.068466, L = 0.9346. Females: a0 = -12.055901, a1 = 2.621579, a2 = -0.035975, p0 = -2.310148, p1 = 0.120428, L = 0.899. Height is in cm, age in years, ln is the natural log, and the splines are small age adjustments from the GLI lookup table.
This is the LMS method: it models the middle value (M), spread (S) and skew (L) of healthy lung function, so the limits follow the real shape of the data. These are the Global Lung Function Initiative (GLI) Global equations, built from 74,185 healthy people¹.
How This Calculator Computes Your Result
Enter your sex, age (3 to 95) and height in cm or feet and inches (1 inch = 2.54 cm). Children can use a decimal age such as 8.5, as the GLI calculator does⁵. The age adjustments are listed every quarter year, and the tool blends the two nearest rows. You get predicted FVC, the LLN and the healthy range (5th to 95th percentile) in liters to 2 decimals. Add your measured FVC in liters to also see percent predicted, a z-score, your percentile and a band. The band comes from the z-score, never from percent predicted.
What Your Result Means
A z-score shows how far your FVC sits from the average for healthy people like you. The LLN is the 5th percentile, a z-score of -1.645, and the grades below it come from the 2022 ERS/ATS standard for reading lung function tests³.
Your z-score | Percentile | Band |
1.65 or higher | Above the 95th | Above the usual range |
-1.64 to 1.64 | 5th to 95th | Within the expected range |
-1.65 to -2.50 | Below the 5th | Below LLN, mild |
-2.51 to -4.00 | Below the 5th | Below LLN, moderate |
Below -4.00 | Below the 5th | Below LLN, severe |
By design, 5 in 100 healthy people score below the LLN. A result in the normal range does not rule out disease, and results close to the LLN need caution³.
Predicted FVC by Age and Height
Predicted FVC in liters, with the LLN in brackets¹.
Age | Male 170 cm (5 ft 7 in) | Male 180 cm (5 ft 11 in) | Female 160 cm (5 ft 3 in) | Female 170 cm (5 ft 7 in) |
20 | 4.45 (3.50) | 5.20 (4.08) | 3.35 (2.60) | 3.93 (3.05) |
30 | 4.50 (3.50) | 5.26 (4.10) | 3.40 (2.62) | 3.98 (3.08) |
40 | 4.34 (3.34) | 5.07 (3.91) | 3.30 (2.51) | 3.87 (2.95) |
50 | 4.12 (3.13) | 4.81 (3.66) | 3.10 (2.31) | 3.63 (2.71) |
60 | 3.85 (2.90) | 4.50 (3.39) | 2.86 (2.08) | 3.35 (2.44) |
70 | 3.59 (2.67) | 4.19 (3.12) | 2.64 (1.87) | 3.09 (2.19) |
80 | 3.36 (2.48) | 3.93 (2.90) | 2.45 (1.69) | 2.87 (1.98) |
At a fixed height, predicted FVC peaks at about age 25 in males and 27 to 28 in females, then falls slowly. Weight is not part of the equations.
How Spirometry Measures Vital Capacity
Your FVC is only as good as the test behind it. The ATS/ERS spirometry standard describes the forced blow in four parts: breathe in fully, blast the air out, keep blowing until no more comes out (up to 15 seconds) while staying upright, then breathe back in fully⁴. The test needs at least three good blows, and for anyone over 6 the two largest FVC values should be within 0.150 L of each other⁴. Height is measured without shoes, feet together⁴. Stopping early or not filling your lungs first makes FVC look lower than it is.
Why Percent Predicted Can Mislead
Many older charts call any FVC under 80% of predicted abnormal. The 2022 ERS/ATS standard strongly discourages the same 80% cutoff for FEV1, because percent predicted ignores how normal variation changes with age³. Normal spread changes with age and sex. With the GLI Global equations¹, the LLN sits at about 77% of predicted for a 40-year-old man and about 71% for a 70-year-old woman. So a 175 cm, 40-year-old man with an FVC of 3.62 L is at 77% of predicted yet inside the normal range.
Why the Equations Are Race-Neutral
Older equations gave a different predicted value by race. In 2023 the American Thoracic Society recommended race-neutral average equations and named GLI Global as one². Its predicted values sit close to the earlier GLI 2012 equations, but its limits of normal are wider¹. Some labs still use older equations, so a lab report may show a slightly different predicted value.
Predicted FVC and Lower Limit of Normal by Age
Pick a sex and height. The solid line is the predicted average and the dashed line is the lower limit of normal (5th percentile).
- Predicted FVC
- Lower limit of normal
Show data table
| Age (years) | Predicted FVC (L) | Lower limit of normal (L) |
|---|---|---|
| 20 years | 4.45 | 3.50 |
| 30 years | 4.50 | 3.50 |
| 40 years | 4.34 | 3.34 |
| 50 years | 4.12 | 3.13 |
| 60 years | 3.85 | 2.90 |
| 70 years | 3.59 | 2.67 |
| 80 years | 3.36 | 2.48 |
A Note on Accuracy
The predicted value is an average, healthy people vary widely, and data above age 90 are thin¹. Your measured FVC depends on effort, coaching and equipment. Spirometry alone cannot diagnose a lung condition, and a low FVC does not prove the lungs are restricted without lung volume tests³. This tool predicts FVC only, not slow vital capacity, FEV1 or peak flow.
Frequently Asked Questions
What is a normal vital capacity?
It depends mainly on height, age and sex: a 40-year-old, 175 cm man has a predicted FVC of 4.70 L (normal down to 3.62 L), and a 40-year-old, 162 cm woman 3.41 L (normal down to 2.60 L)¹. Any value at or above your LLN is in the normal range³.
What is a good FVC percent predicted?
There is no single good percent, because the normal limit sits at a different percent for each age and sex. A result counts as normal when it is above the lower limit of normal (z-score above -1.645), not when it passes 80%³.
What is the difference between vital capacity and FVC?
Both are the most air you can breathe out after a full breath in. FVC uses a hard, fast blow and slow vital capacity a relaxed one; FVC is the one on most spirometry reports⁴.
Does a low FVC mean I have lung disease?
Not on its own. Lung function tests alone should not be used to diagnose a specific condition, and 5 in 100 healthy people fall below the LLN³.
Sources
A Race-neutral Approach to the Interpretation of Lung Function Measurements, Bowerman et al., 2023
Race and Ethnicity in Pulmonary Function Test Interpretation, American Thoracic Society (Bhakta et al.), 2023
ERS/ATS Technical Standard on Interpretive Strategies for Routine Lung Function Tests, Stanojevic et al., 2022
Standardization of Spirometry 2019 Update, Graham et al., 2019
GLI Calculator Help, Global Lung Function Initiative