FEV1/FVC Ratio (Tiffeneau Index)
Page updated: Evidence reviewed: What this means
FEV1/FVC is the ratio of the largest reported first-second volume to the largest reported forced vital capacity from a spirometry test. GLI-2012 fitted a dedicated reference equation to this ratio rather than dividing its separate predicted FEV1 and FVC values. These tables are an archival reproduction of the ethnicity-specific coefficient set the source labels "Caucasian"; current ATS/ERS guidance favours race-neutral equations. Each age band is one equation calculation at the bracket midpoint and one NHANES median height, not a pooled distribution across the band. The 80+ row represents age 85 and should not be extrapolated beyond age 95. See the derivation and assumptions.
How to Perform This Test (Protocol)
- Equipment
-
- 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, then begin forced expiration without hesitation; the interval from full inspiration to time zero should be no more than 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 an FVC within the repeatability tolerance of or greater than the largest previous FVC.
- The person inhales fully at the end of the manoeuvre.
- The goal is at least three acceptable FEV1 and three acceptable FVC measurements, with enough recovery between efforts; additional attempts may be needed.
- Scoring
The largest acceptable FEV1 is divided by the largest acceptable FVC, even when they come from different efforts. For people older than 6 years, repeatability requires the two largest values of each index to differ by less than 0.150 L. At age 6 or younger, the tolerance is less than 0.100 L or 10% of the highest value, whichever is greater. The 2019 standard reports a measured ratio to two decimal places; this reference grid retains three decimals to show the fitted percentile differences.
- Notes
Acceptability is judged separately for FEV1 and FVC, so one effort may contribute to only one index. A cough in the first second invalidates FEV1, while early termination can invalidate FVC. The full standard includes contraindication screening, infection control, device quality assurance, operator coaching, and session grading that this summary omits. Spirometry is a supervised clinical test, not a do-it-yourself maximal-effort exercise.
Data source: Quanjer et al. (GLI-2012) About this study
See also: Graham et al. (ATS/ERS 2019) About this study
Reference population: 74,187 healthy lifelong nonsmokers aged 3-95 years in four fitted groups; 57,395 were in the source-labelled Caucasian group
FEV1/FVC Ratio (Tiffeneau Index) Norms Chart by Age and Sex
| Age | Sex | Percentile | ||||
|---|---|---|---|---|---|---|
| 5th | 25th | 50th | 75th | 95th | ||
| 5-9 | Male | 0.778 | 0.851 | 0.894 | 0.933 | 0.982 |
| Female | 0.800 | 0.870 | 0.909 | 0.943 | 0.985 | |
| 10-14 | Male | 0.755 | 0.822 | 0.864 | 0.902 | 0.952 |
| Female | 0.783 | 0.852 | 0.892 | 0.927 | 0.971 | |
| 15-19 | Male | 0.747 | 0.819 | 0.864 | 0.906 | 0.961 |
| Female | 0.780 | 0.851 | 0.893 | 0.931 | 0.978 | |
| 20-29 | Male | 0.727 | 0.798 | 0.843 | 0.884 | 0.938 |
| Female | 0.749 | 0.822 | 0.866 | 0.905 | 0.956 | |
| 30-39 | Male | 0.713 | 0.778 | 0.819 | 0.857 | 0.908 |
| Female | 0.724 | 0.794 | 0.837 | 0.876 | 0.928 | |
| 40-49 | Male | 0.694 | 0.759 | 0.800 | 0.839 | 0.890 |
| Female | 0.704 | 0.771 | 0.813 | 0.853 | 0.905 | |
| 50-59 | Male | 0.671 | 0.741 | 0.785 | 0.827 | 0.884 |
| Female | 0.685 | 0.755 | 0.800 | 0.842 | 0.898 | |
| 60-69 | Male | 0.644 | 0.721 | 0.771 | 0.818 | 0.883 |
| Female | 0.663 | 0.740 | 0.789 | 0.835 | 0.897 | |
| 70-79 | Male | 0.616 | 0.702 | 0.758 | 0.812 | 0.885 |
| Female | 0.638 | 0.723 | 0.778 | 0.830 | 0.899 | |
| 80+ | Male | 0.592 | 0.686 | 0.747 | 0.807 | 0.890 |
| Female | 0.615 | 0.709 | 0.769 | 0.826 | 0.903 | |
What to expect by age group
At the age-25 calculation point, the middle 50% spans 0.798 to 0.884 for men and 0.822 to 0.905 for women. The equation's median ratio generally declines across adult ages. Percentile position alone is not a diagnosis and the ratio is not a higher-is-better performance score; it must be interpreted with FEV1, FVC, test quality, and clinical context.
| Age | Males | Females |
|---|---|---|
| 5-9 | 0.851 to 0.933 | 0.870 to 0.943 |
| 10-14 | 0.822 to 0.902 | 0.852 to 0.927 |
| 15-19 | 0.819 to 0.906 | 0.851 to 0.931 |
| 20-29 | 0.798 to 0.884 | 0.822 to 0.905 |
| 30-39 | 0.778 to 0.857 | 0.794 to 0.876 |
| 40-49 | 0.759 to 0.839 | 0.771 to 0.853 |
| 50-59 | 0.741 to 0.827 | 0.755 to 0.842 |
| 60-69 | 0.721 to 0.818 | 0.740 to 0.835 |
| 70-79 | 0.702 to 0.812 | 0.723 to 0.830 |
| 80+ | 0.686 to 0.807 | 0.709 to 0.826 |
Detailed Breakdowns
Select an age group and sex below for detailed percentile charts.
Frequently Asked Questions
What is a typical FEV1/FVC ratio?
There is no single typical ratio. The expected value and lower limit of normal change with age, sex, and the selected reference equation. Fixed cutoffs such as 0.70 can classify people differently from an age-adjusted lower limit, especially at younger and older ages. The 2022 ERS/ATS interpretive standard uses z-scores and requires the ratio to be read with FEV1, FVC, test quality, and clinical context.
Why does the FEV1/FVC ratio decline with age?
In the GLI-2012 equation, FEV1 changes with age somewhat differently from FVC, so their fitted ratio generally declines across adulthood. This page shows calculations at ages 25, 35, and so on; it does not follow the same people over time and should not be read as a personal rate of decline. Individual interpretation still depends on the full spirometry report and clinical context.
Why isn't a higher FEV1/FVC ratio always better?
The ratio is not a performance score. A low ratio can support classification of an obstructive ventilatory pattern. A preserved or high ratio with reduced FVC does not confirm restriction; total lung capacity is required for that determination. Percentile position alone therefore does not indicate health, and spirometry reports include FEV1, FVC, the ratio, and quality information together.
Where does this data come from?
The values are calculated from the dedicated GLI-2012 LMS equation for FEV1/FVC. The final four-group model used 74,187 healthy lifelong nonsmokers; this site sets the group adjustments to the source-labelled "Caucasian" coefficients and evaluates one exact age and NHANES median height per displayed bracket. Current ATS/ERS guidance favours race-neutral equations, so this is an archival reproduction rather than a clinical calculator. See the methodology page and source review for the details.
FEV1 or FEV1/FVC: which should I look at?
FEV1 is the volume exhaled in the first second, in litres. FEV1/FVC divides the largest reported FEV1 by the largest reported FVC and describes the proportion exhaled in that first second. They answer different questions, and a standard report includes both. See the FEV1 page and FVC page.