FEV1 (Lung Function)
FEV1 (also written FEV₁) is the volume of air a person can forcefully exhale in one second during a spirometry test, the standard measure of airway obstruction and a key marker in diagnosing and monitoring COPD and asthma. Higher values indicate greater lung function. These percentiles reproduce the GLI-2012 reference equations using the coefficient set the source labels "Caucasian" (the largest subgroup in the GLI dataset), evaluated at median heights for each age group from NHANES reference data. They therefore inherit that equation's population model. Results vary by height, and the GLI-2012 model also varies its predictions by ethnicity; see the FAQ below. The derivation method is documented on the FEV1 methodology page.
How to Perform This Test (Protocol)
- Equipment
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- Spirometer meeting ATS/ERS 2019 accuracy and calibration-verification requirements
- Disposable mouthpiece, with a bacterial/viral filter where used
- Nose clip
- Chair with arms (testing is performed seated unless there is a documented reason not to)
- Protocol Steps
-
- The person sits upright with feet flat on the floor, wearing a nose clip, and seals their lips around the mouthpiece.
- They breathe normally through the mouthpiece until a stable end-expiratory level is reached.
- They inhale completely and rapidly to total lung capacity, with a pause at full inflation of under two seconds.
- They blast air out as forcefully and as fast as possible, and continue exhaling without interruption.
- Exhalation continues until an end of forced expiration criterion is met: a plateau of less than 0.025 L change in volume over at least one second, or 15 seconds of forced expiration, or (for people who cannot reach a plateau) an FVC within the repeatability tolerance of the largest previous FVC.
- The person inhales fully at the end of the manoeuvre.
- At least three acceptable manoeuvres are obtained, with a rest between efforts.
- Scoring
FVC is the total volume of air exhaled during the forced manoeuvre, reported in litres at BTPS. The largest FVC from any acceptable manoeuvre is reported, and the largest FEV1 likewise, even if they come from different efforts. A test is repeatable when the two largest FVC values differ by no more than 0.150 L, and the two largest FEV1 values likewise. For people aged 6 years and under the tolerance is 0.100 L or 10% of the highest value, whichever is greater.
- Notes
The 2019 standard removed the older six-second minimum exhalation time; duration is judged by the end of forced expiration criteria above, not by a fixed clock. Acceptability is judged separately for each index, so one manoeuvre may contribute a valid FVC and an invalid FEV1. A cough in the first second makes FEV1 unusable but can leave FVC acceptable. Glottic closure depends on timing: within the first second it invalidates both FEV1 and FVC, while after the first second it invalidates FVC but can leave FEV1 usable. Manoeuvres with a hesitant or false start, an obstructed mouthpiece, or evidence of a leak are not usable for either index.
Data source: Quanjer et al. (GLI-2012) About this study
See also: Graham et al. (ATS/ERS 2019) About this study
Reference population: Males and females aged 3-95 years from 33 countries; 74% Caucasian, with African American, North East Asian, and South East Asian subgroups
FEV1 (Lung Function) Norms Chart by Age and Sex (L)
| Age | Sex | Percentile | ||||
|---|---|---|---|---|---|---|
| 5th | 25th | 50th | 75th | 95th | ||
| 5-9 | Male | 1.09 | 1.25 | 1.36 | 1.48 | 1.64 |
| Female | 1.03 | 1.18 | 1.29 | 1.39 | 1.54 | |
| 10-14 | Male | 2.00 | 2.28 | 2.48 | 2.67 | 2.95 |
| Female | 2.05 | 2.34 | 2.54 | 2.74 | 3.02 | |
| 15-19 | Male | 3.53 | 4.03 | 4.38 | 4.72 | 5.21 |
| Female | 2.67 | 3.05 | 3.31 | 3.57 | 3.94 | |
| 20-29 | Male | 3.66 | 4.19 | 4.55 | 4.90 | 5.40 |
| Female | 2.62 | 3.00 | 3.26 | 3.52 | 3.88 | |
| 30-39 | Male | 3.39 | 3.91 | 4.26 | 4.61 | 5.11 |
| Female | 2.49 | 2.85 | 3.11 | 3.35 | 3.71 | |
| 40-49 | Male | 3.13 | 3.63 | 3.97 | 4.31 | 4.78 |
| Female | 2.26 | 2.62 | 2.86 | 3.11 | 3.45 | |
| 50-59 | Male | 2.78 | 3.28 | 3.62 | 3.95 | 4.41 |
| Female | 1.99 | 2.34 | 2.58 | 2.82 | 3.16 | |
| 60-69 | Male | 2.35 | 2.85 | 3.18 | 3.50 | 3.96 |
| Female | 1.68 | 2.03 | 2.26 | 2.49 | 2.82 | |
| 70-79 | Male | 1.95 | 2.43 | 2.75 | 3.06 | 3.50 |
| Female | 1.38 | 1.71 | 1.93 | 2.15 | 2.46 | |
| 80+ | Male | 1.64 | 2.10 | 2.41 | 2.71 | 3.12 |
| Female | 1.12 | 1.43 | 1.64 | 1.84 | 2.13 | |
What to expect by age group
| Age | Males | Females |
|---|---|---|
| 5-9 | 1.25 to 1.48 | 1.18 to 1.39 |
| 10-14 | 2.28 to 2.67 | 2.34 to 2.74 |
| 15-19 | 4.03 to 4.72 | 3.05 to 3.57 |
| 20-29 | 4.19 to 4.90 | 3.00 to 3.52 |
| 30-39 | 3.91 to 4.61 | 2.85 to 3.35 |
| 40-49 | 3.63 to 4.31 | 2.62 to 3.11 |
| 50-59 | 3.28 to 3.95 | 2.34 to 2.82 |
| 60-69 | 2.85 to 3.50 | 2.03 to 2.49 |
| 70-79 | 2.43 to 3.06 | 1.71 to 2.15 |
| 80+ | 2.10 to 2.71 | 1.43 to 1.84 |
Detailed Breakdowns
Select an age group and sex below for detailed percentile charts and distribution labels.
Frequently Asked Questions
What is a normal FEV1?
There is no single normal FEV1. Expected values depend on age, sex, and height, which is why spirometry is interpreted against a reference equation rather than a fixed number. The conventional boundary is the lower limit of normal (LLN), the 5th percentile of the reference population, equivalent to a z-score of -1.645. A value above the LLN sits within the reference range for that age, sex, and height. The older rule of thumb that anything above 80% of the predicted value is normal is no longer recommended: the ERS/ATS interpretive standard advises against fixed percentage-of-predicted thresholds because they misclassify results at the extremes of age and height (Stanojevic et al. 2022, DOI 10.1183/13993003.01499-2021). Interpret an individual result from the full spirometry report with a qualified clinician.
Does ethnicity affect FEV1?
The GLI-2012 reference equations vary their predictions by ethnicity. Relative to the subgroup GLI labels "Caucasian," GLI-2012 (Table 3) reports values approximately 10-15% lower for the African American group, approximately 4% lower for the North East Asian group, and approximately 9-12% lower for the South East Asian group. The percentiles on this site use the GLI "Caucasian" coefficients, the largest subgroup in the dataset (81% of males, 86% of females). The full set of GLI-2012 ethnicity coefficients can be applied at the GLI calculator (gli-calculator.ersnet.org). In a 2023 official statement, the American Thoracic Society recommended against race- and ethnicity-specific reference equations for spirometry interpretation, favouring race-neutral reference values (Bhakta et al. 2023, DOI 10.1164/rccm.202302-0310ST; endorsed by the European Respiratory Society). An individual result should be interpreted from the full spirometry report with a qualified clinician rather than by selecting an ethnicity adjustment yourself.
Why does height affect FEV1?
Taller people have larger lungs and airways, so they can exhale more air in one second. FEV1 scales approximately with the square of height. The percentiles shown here are computed at the median height for each age and sex bracket from NHANES data. If you are notably taller or shorter than average, your expected FEV1 will be higher or lower accordingly.
What is the difference between FEV1 and FVC?
FVC (forced vital capacity) is the total volume of air exhaled during a maximal forced breath. FEV1 is the portion exhaled in the first second. A low FEV1/FVC ratio supports an obstructive pattern. A preserved ratio with a reduced FVC can suggest possible restriction, but total lung capacity is needed to confirm it. See the FEV1/FVC ratio page for percentiles of the ratio across age and sex. See the FVC page for the distribution of forced vital capacity across age and sex.