How this instrument works
Total lung capacity (TLC) is the full volume of air the lungs hold at maximum inflation, including the residual volume that stays behind even after the most forceful exhale. That last part matters: TLC is not the same measurement as vital capacity (VC), the air a person can actively move in and out. A simple spirometer, which measures airflow, can capture VC directly but cannot see the residual air left in the lungs, so TLC itself is most accurately measured by body plethysmography — a sealed-booth technique that infers lung volume from pressure changes — or by gas-dilution methods, not by spirometry alone.
This calculator uses the ERS/ECCS 1993 height-only reference equations for predicted TLC: 7.99 x height(m) minus 7.08 for men, and 6.60 x height(m) minus 5.79 for women. These equations come from the European Respiratory Society / European Community for Steel and Coal 1993 reference-value report on lung volumes and forced ventilatory flows, and they remain widely cited in clinical and physiology references as a simple height-based predicted-TLC formula decades after publication.
The equations were derived from a Caucasian reference population and validated across roughly ages 18-70, though the same coefficients are commonly applied in clinical use up through about age 90 given the absence of a more targeted alternative for that range. They do not adjust for ethnicity, and neither, for TLC specifically, does the current clinical standard: a newer Global Lung Function Initiative (GLI) reference for static lung volumes (Hall et al., European Respiratory Journal 2021) supersedes the 1993 equations but remains derived from individuals of European ancestry, since its authors found insufficient non-European data to build multi-ethnic lung-volume equations. That 2021 standard is a separate, later publication from the better-known GLI-2012 spirometry reference values, which do support multiple ethnic groups but only for airflow measures such as FEV1 and FVC, not for TLC. The 2021 standard is also built on large spline and lookup-table coefficients that this calculator's simple-expression engine cannot encode, which is why the older, simpler 1993 height-only equations were used here instead — a simplicity trade-off, not a claim of superior accuracy or ethnicity coverage.
A sourcing note: the 1993 ERS/ECCS supplement itself (Quanjer et al., European Respiratory Journal 1993) is an older report that is not freely indexed online and could not be accessed directly while building this page. The two coefficient pairs above were instead cross-validated against the widely cited Stocks & Quanjer 1995 restatement of the same reference values, which agrees exactly on every coefficient used here — the same secondary-sourcing approach this site's APACHE II and SAPS II pages disclose for their own paywalled or hard-to-access primary sources.
- Enter Height (m) — standing height in metres, for example 1.75 for someone 175 cm tall.
- Set Sex is female to Yes or No; the calculator applies a different pair of coefficients for each, since the two reference equations were derived separately by sex.
- Read Predicted total lung capacity (L) — the expected TLC for a person of that height and sex under the 1993 reference equations, in litres.
- Treat the result as a population-average reference point, not a personal diagnosis — an actual TLC is measured by body plethysmography or gas dilution, not calculated from height alone.
A 1.75 m man's predicted TLC
A man stands 1.75 m tall. Sex is female is set to No, so the men's equation applies: predicted TLC = 7.99 x 1.75 - 7.08. Multiplying first, 7.99 x 1.75 = 13.9825, then subtracting 7.08 gives 13.9825 - 7.08 = 6.9025 L.
The calculator reports a predicted total lung capacity of 6.90 L. That figure is a population-average expectation for a 1.75 m man under the 1993 reference equations, not this particular individual's measured TLC — an actual value would come from body plethysmography or a gas-dilution lung-function test, and could reasonably sit above or below the predicted figure even in a healthy person.
Questions
What is total lung capacity (TLC) and how does it differ from vital capacity?
Total lung capacity is the full volume of air the lungs hold at maximum inflation, including air that cannot be exhaled at all — the residual volume. Vital capacity (VC) is the air that can actively move in and out on a forceful breath, and it excludes that residual volume. Because a standard spirometer measures airflow, it can capture VC directly but cannot see residual air, so TLC itself is normally measured by body plethysmography or a gas-dilution technique, not by spirometry alone.
Why does this calculator only ask for height and sex?
The ERS/ECCS 1993 reference equations used here are height-only formulas: predicted TLC = 7.99 x height(m) - 7.08 for men and 6.60 x height(m) - 5.79 for women. Height correlates strongly with lung size in the reference population these equations were built from, which is why a single measurement plus sex is enough to produce a predicted value — though it also means the equations cannot account for anything else that affects an individual's actual lung volume, such as age, body build, or health status.
Why does this tool use the 1993 equations instead of newer GLI reference values?
The current clinical standard for predicted static lung volumes, including TLC, is a newer Global Lung Function Initiative reference (Hall et al., European Respiratory Journal 2021) — a later, separate paper from the better-known GLI-2012 values, which cover only spirometric measures like FEV1 and FVC, not TLC. That 2021 standard uses spline and lookup-table coefficients this calculator's simple-expression engine cannot encode. The older ERS/ECCS 1993 height-only equations were used here instead because they reduce to two coefficients per sex — a simplicity trade-off, not a claim of superior accuracy.
Does this predicted TLC account for ethnicity?
No. The ERS/ECCS 1993 equations were derived from a Caucasian reference population and were not built with ethnicity-specific adjustments. Even the current standard for predicted TLC — the 2021 Global Lung Function Initiative static lung volumes reference (Hall et al.) — remains restricted to individuals of European ancestry, since its authors found insufficient non-European data to build multi-ethnic lung-volume equations; only the separate, spirometry-only GLI-2012 values support multiple ethnic groups, and those do not predict TLC. See the previous answer for why the older 1993 equations were used here instead.
What age range do these equations apply to?
The 1993 reference equations were derived and validated on a population spanning roughly ages 18 to 70. In practice, clinicians commonly extend the same coefficients up through about age 90 in the absence of a more targeted height-only alternative for older adults, but predictions outside the original 18-70 validation range carry more uncertainty than predictions within it.
How reliable is the coefficient pair behind this calculator?
The primary 1993 ERS/ECCS report (Quanjer et al., European Respiratory Journal, Suppl. 16) is an older publication that is not freely indexed online and could not be read directly while building this page. The two coefficient pairs used here were instead cross-validated against the widely cited Stocks & Quanjer 1995 restatement of the same reference values, which agrees exactly on every coefficient. This is the same secondary-sourcing approach this site discloses on its APACHE II and SAPS II pages for their own hard-to-access primary sources.
Can this calculator replace a real pulmonary function test?
No. This tool reproduces one published height-based formula so a predicted, population-average TLC is visible for reference and comparison — it does not measure anyone's actual lung volume. An actual TLC comes from body plethysmography or a gas-dilution test, interpreted alongside spirometry and the rest of a pulmonary function test by a clinician who knows the patient's history. Any concern about lung function or a result that seems unusual belongs in front of that clinician, not this page.
Why might my actual TLC differ from the predicted value here?
The predicted value is a population average for a given height and sex under the 1993 reference equations — real individuals vary around that average even when healthy, due to factors the height-only formula cannot capture, such as chest and torso proportions, body build, altitude of residence, smoking history, or lung disease. A meaningful comparison requires an actual measured TLC from plethysmography or gas dilution, expressed as a percentage of this kind of predicted value, which is how pulmonary function tests are typically interpreted in practice.
References
- Quanjer PH et al. Lung volumes and forced ventilatory flows. Eur Respir J. 1993;6(Suppl 16):5-40
- Stocks J, Quanjer PH. Reference values for lung volumes. Eur Respir J. 1995;8:492-506
- Quanjer PH et al. Multi-ethnic reference values for spirometry (GLI-2012). Eur Respir J. 2012;40:1324-1343
- Hall GL et al. GLI reference values for static lung volumes (European ancestry). Eur Respir J. 2021;57:2000289
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.