FEV1/FVC Ratio (Tiffeneau Index)

The FEV1/FVC ratio (also known as the Tiffeneau or Tiffeneau-Pinelli index) is the fraction of total exhaled lung volume (FVC) expelled in the first second of a forced exhalation (FEV1). It is reported alongside FEV1 and FVC in a standard spirometry session. Percentiles here are derived directly from the GLI-2012 LMS equation for FEV1/FVC, applied at NHANES median heights for each age and sex. The derivation method is documented on the FEV1/FVC ratio methodology page. This page reports where a value sits in the GLI-2012 reference population. For interpretation of an individual result, see a clinician with the full spirometry report.

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
  1. The person sits upright with feet flat on the floor, wearing a nose clip, and seals their lips around the mouthpiece.
  2. They breathe normally through the mouthpiece until a stable end-expiratory level is reached.
  3. They inhale completely and rapidly to total lung capacity, with a pause at full inflation of under two seconds.
  4. They blast air out as forcefully and as fast as possible, and continue exhaling without interruption.
  5. 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.
  6. The person inhales fully at the end of the manoeuvre.
  7. 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) (2012) · n=97.8K About this study

See also: Graham et al. (ATS/ERS 2019) (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/FVC Ratio (Tiffeneau Index) Respiratory

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

Among adults in their 20s, the middle 50% measure 0.798 to 0.884 for men and 0.822 to 0.905 for women. The ratio is highest in childhood, declines steadily through adulthood, and by the 70s the median falls to about 0.76 for men and 0.78 for women. The ratio is not higher-is-better: low values and very high values combined with low absolute FVC carry different meanings, so the percentile position alone does not indicate health on this metric.

Typical range (25th to 75th percentile) by age group
Age MalesFemales
5-9 0.851 to 0.9330.870 to 0.943
10-14 0.822 to 0.9020.852 to 0.927
15-19 0.819 to 0.9060.851 to 0.931
20-29 0.798 to 0.8840.822 to 0.905
30-39 0.778 to 0.8570.794 to 0.876
40-49 0.759 to 0.8390.771 to 0.853
50-59 0.741 to 0.8270.755 to 0.842
60-69 0.721 to 0.8180.740 to 0.835
70-79 0.702 to 0.8120.723 to 0.830
80+ 0.686 to 0.8070.709 to 0.826

Detailed Breakdowns

Select an age group and sex below for detailed percentile charts.

Males
5-910-1415-1920-2930-3940-4950-5960-6970-7980+
Females
5-910-1415-1920-2930-3940-4950-5960-6970-7980+
Age trend (percentiles)

Frequently Asked Questions

What is a typical FEV1/FVC ratio?

There is no single 'typical' number; the expected ratio declines with age. In the GLI-2012 reference population, a 25-year-old man has a median FEV1/FVC ratio around 0.84, falling to about 0.77 by his 60s. Women run slightly higher at every age, from about 0.87 in the 20s to 0.79 in the 60s. A threshold around 0.70 is widely cited as a screening number, but interpretation of an individual value also depends on the absolute FVC and FEV1. This page reports population position only.

Why does the FEV1/FVC ratio decline with age?

Both FEV1 and FVC fall with age, but FEV1 falls faster. Aging lungs lose elastic recoil, the small airways become less stable, and exhalation in the first second is disproportionately reduced relative to total exhaled volume. The result is a steady decline in the median ratio from about 0.84 in men's 20s to around 0.75 by their 80s, and from 0.87 to 0.77 in women across the same span. This age pattern is observed in the GLI-2012 reference population of healthy non-smokers; interpretation of an individual result still depends on FEV1, FVC, and clinical context.

Why isn't a higher FEV1/FVC ratio always better?

Unlike FEV1 alone, the ratio is not 'higher is better'. Low ratios are associated with obstructive lung patterns such as asthma and COPD. Very high ratios combined with a low absolute FVC are associated with restrictive patterns. A percentile position on its own does not indicate health on this metric, which is why spirometry reports always include FEV1, FVC, and the ratio together.

Where does this data come from?

The percentiles are computed directly from the Global Lung Function Initiative 2012 (GLI-2012) LMS equation for FEV1/FVC, published by Quanjer et al. in the European Respiratory Journal (DOI 10.1183/09031936.00080312) using data from 97,759 healthy non-smokers across 33 countries. The equation is applied at NHANES median heights for each age and sex bracket, using the coefficient set GLI labels "Caucasian" (the largest subgroup, 81% of males and 86% of females in the GLI dataset). 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). Interpret an individual result from the full spirometry report with a qualified clinician. See the methodology page for the full derivation, including the coefficient table and the male/female L-equation difference.

FEV1 or FEV1/FVC: which should I look at?

FEV1 is the absolute volume of air exhaled in the first second, in litres. The FEV1/FVC ratio is the fraction of total exhaled volume that comes out in that first second. They measure different things and a standard spirometry report includes both. The FEV1 norms are on the FEV1 page.

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