Lung Capacity Calculator

Band	% Predicted
Restrictive pattern	< 80%
Normal range	80% – 120%
Elevated (possible hyperinflation)	> 120%

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Walk-through

How to Use This Calculator

3 steps

1

Enter age, height, and sex

Type your age in years, enter your height (toggle cm/in as needed), and select your sex. These three values compute your predicted total lung capacity instantly using the Crapo/Quanjer regression equation.

2

Add a measured TLC if you have one

If a pulmonary function test (plethysmography or gas dilution — not spirometry alone) has already given you a measured TLC in liters, enter it in the optional field to see your percent predicted and whether it falls in the restrictive, normal, or elevated range.

3

Check the validity range before relying on the result

The regression was studied in adults aged 18-70 with height 1.55-1.95 m (men) or 1.45-1.80 m (women). Outside that range, treat the predicted value as a rough estimate and check the Interpretation tab for a flag.

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Reference

Formula & Methodology

2 formulas

Predicted TLC — men

TLC (L) = 7.99 × height (m) − 7.08

Crapo RO et al. 1982, standardized by Quanjer PH et al., ERS 1993. Height is the only anthropometric term; age and weight are not regression inputs.

Predicted TLC — women

TLC (L) = 6.60 × height (m) − 5.79

Same source as the male equation. Validity range: age 18-70y, height 1.45-1.80 m. Age outside 18-70 or height outside the studied range triggers a validity note rather than blocking the result.

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High YMYL

Trust, Methodology & Sources

Reviewed by Calculover Editorial Review · Updated 2026-07-22 · 2 sources

Editorial accountability

Author: Calculover Editorial Team - Editor

Owner: Calculover Editorial Team - Editorial owner

Reviewer: Calculover Editorial Review - Medical-source review

Last reviewed: 2026-07-22

Last verified: 2026-07-22

Data effective: 2026-07-22

Methodology

Predicted total lung capacity uses the height-and-sex regression from Crapo RO, Morris AH, Gardner RM et al., 'Lung volumes in healthy nonsmoking adults,' Bulletin Europeen de Physiopathologie Respiratoire 1982;18:419-425, standardized in Quanjer PH et al., 'Lung volumes and forced ventilatory flows,' European Respiratory Journal 1993;6(Suppl 16):5-40. Men use TLC (L) = 7.99 × height (m) − 7.08; women use TLC (L) = 6.60 × height (m) − 5.79. Age is used only to flag whether the input falls within the 18-70 year studied range, not as a regression coefficient. When a measured TLC is entered, percent predicted is measured ÷ predicted × 100, classified as restrictive (< 80%), normal (80-120%), or elevated (> 120%) per standard ATS/ERS convention.

Assumption: Height is entered as standing adult height without shoes.

Assumption: Sex is used as a binary male/female coefficient because the source regression only published two coefficient sets.

Assumption: Measured TLC, when provided, is assumed to come from plethysmography or a gas-dilution method, not spirometry alone.

Limitations & guidance

Spirometry alone cannot measure total lung capacity or residual volume — a true TLC measurement requires body plethysmography or a gas-dilution method (helium dilution or nitrogen washout); this calculator does not perform that measurement, it only compares a user-supplied measured value against a predicted reference.

The regression was derived from a healthy nonsmoking adult reference population studied at ages 18-70; it may be less accurate outside that age range or outside the studied height range.

This tool does not diagnose restrictive or obstructive lung disease — a full diagnosis requires a clinician's review of the complete PFT panel, including DLCO and flow-volume loops, alongside clinical history and imaging.

Professional guidance: This calculator is for educational purposes only and is not medical advice. It does not diagnose any lung condition. Discuss any pulmonary function test results with a qualified physician or pulmonologist.

Primary sources

Crapo RO, Morris AH, Gardner RM. Lung volumes in healthy nonsmoking adults. Bulletin Europeen de Physiopathologie Respiratoire, 1982. - Bull Eur Physiopathol Respir 1982;18:419-425

Quanjer PH, Tammeling GJ, Cotes JE, et al. Lung volumes and forced ventilatory flows. Official Statement of the European Respiratory Society. - Eur Respir J 1993;6(Suppl 16):5-40

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Glossary

Key Terms Explained

7 terms

Total lung capacity The volume of air in the lungs after a maximal inspiration — the sum of all four lung volumes (tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume), reported in liters.

TLC The standard abbreviation for total lung capacity, the value this calculator predicts and compares against a measured pulmonary function test result.

Pulmonary function test A group of breathing tests — spirometry, body plethysmography, and gas-dilution methods — that measure how much air the lungs hold and how quickly air moves in and out of them.

Restrictive pattern A pulmonary function test pattern where total lung capacity falls below 80% predicted, indicating reduced lung volume rather than reduced airflow. Common causes include pulmonary fibrosis, chest wall disease, and neuromuscular weakness.

Plethysmography A body-box pulmonary function test that measures total lung capacity and other lung volumes from pressure changes as a patient breathes inside a sealed chamber. It can capture trapped air that spirometry cannot detect.

Residual volume The air remaining in the lungs after a maximal exhalation. It cannot be measured by spirometry alone — only by plethysmography or a gas-dilution method — which is why spirometry cannot directly measure total lung capacity.

Predicted value The expected normal total lung capacity for a person's height and sex, derived from a reference-population regression equation. It serves as the denominator when computing a percent-predicted comparison against a measured result.

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Scenarios

Real-World Examples

3 worked examples

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Healthy 28-year-old woman

Normal adult female, no measured value entered

Age 28 Height 165 cm Sex Female

At 165 cm, a healthy 28-year-old woman's predicted TLC is 6.60 × 1.65 − 5.79 = 5.10 L. With no measured value entered, this is a baseline reference only — not a diagnosis.

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Adult male with a PFT in hand

Normal percent predicted

Age 45 Height 178 cm Sex Male Measured TLC 6.50 L

Predicted TLC is 7.99 × 1.78 − 7.08 = 7.14 L. A measured TLC of 6.50 L against that predicted value is 91% predicted — within the normal 80-120% band, so this result shows no restrictive pattern by lung volume.

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Patient with suspected pulmonary fibrosis

Restrictive case, below 80% predicted

Age 62 Height 170 cm Sex Male Measured TLC 4.90 L

Predicted TLC is 7.99 × 1.70 − 7.08 = 6.50 L. A measured 4.90 L against that predicted value is about 75% predicted, below the 80% restrictive-pattern threshold — consistent with a restrictive ventilatory defect. A clinician should correlate this with imaging and other PFT findings such as DLCO.

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Deep Dive

Understanding the Lung Capacity Calculator

3 chapters · 4 min read

Total lung capacity (TLC) is one of the core measurements in a pulmonary function test, but a raw liter value only means something in the context of what's expected for a person's height and sex. This calculator predicts that expected value using a well-established regression equation, then compares it against a measured result to help you understand where a pulmonary function test result falls.

How predicted TLC is calculated

Predicted TLC uses the Crapo/Quanjer regression, derived from a healthy nonsmoking adult reference population (Crapo RO et al., 1982, standardized by Quanjer PH et al. in the ERS 1993 Official Statement). The equation uses only height and sex — men use TLC (L) = 7.99 × height (m) − 7.08, and women use TLC (L) = 6.60 × height (m) − 5.79. Age is not a coefficient in this regression; instead, it is used to flag whether your inputs fall within the 18-70 year range the equation was studied on.

Reading your percent predicted

When you enter a measured TLC from a pulmonary function test, the calculator divides it by the predicted value to get a percent predicted. A result below 80% predicted is classified as a restrictive pattern — reduced lung volume rather than reduced airflow. A result between 80% and 120% predicted is considered within the normal range. A result above 120% predicted can reflect hyperinflation, but on its own does not diagnose an obstructive disease; that requires the full flow-volume and airflow picture from a complete PFT panel.

Why this can't replace a real pulmonary function test

Spirometry — the most commonly performed breathing test — cannot measure total lung capacity or residual volume on its own; a true TLC measurement requires body plethysmography or a gas-dilution method such as helium dilution or nitrogen washout. This calculator does not perform that measurement; it only compares a user-supplied measured value against a predicted reference. It also does not diagnose restrictive or obstructive lung disease — that requires a clinician's review of the complete PFT panel, including diffusion capacity (DLCO) and flow-volume loops, alongside clinical history and imaging.

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Questions

Frequently Asked Questions

6 questions

What is the formula for predicted total lung capacity?+

Men: TLC (L) = 7.99 × height (m) − 7.08. Women: TLC (L) = 6.60 × height (m) − 5.79. Both come from Crapo RO et al., Bull Eur Physiopathol Respir 1982;18:419-425, standardized in Quanjer PH et al.'s ERS 1993 Official Statement. Age is not a term in either equation.

Why isn't age used in the calculation itself?+

The Crapo/Quanjer regression was derived from height and sex only — unlike some other spirometry reference equations, it does not include an age coefficient. Age is still useful information, so this calculator uses it to check whether your inputs fall within the 18-70 year range the equation was studied on, flagging the result as a rough estimate if you're outside that range.

What counts as a restrictive pattern on TLC?+

A measured TLC below 80% predicted is the standard ATS/ERS threshold for a restrictive ventilatory pattern. 80% to 120% predicted is considered the normal range, and above 120% predicted can reflect hyperinflation, though that alone does not diagnose an obstructive disease.

Can spirometry alone measure my TLC?+

No. Spirometry cannot measure residual volume — the air left in the lungs after a maximal exhale — so it cannot directly measure total lung capacity. A true TLC measurement requires body plethysmography or a gas-dilution technique such as helium dilution or nitrogen washout.

What if my age or height falls outside the equation's studied range?+

The Crapo/Quanjer equation was validated in adults aged 18-70 with height 1.55-1.95 m (men) or 1.45-1.80 m (women). If your age or height falls outside that range, this calculator still computes a predicted value but flags it on the Interpretation tab as a rough estimate rather than a validated prediction.

How is percent predicted TLC different from percent predicted FVC?+

Percent predicted TLC compares your measured total lung volume — including residual volume, which spirometry cannot capture — against a height-and-sex reference. Percent predicted FVC only reflects the volume you can forcibly exhale after a maximal breath, so the two percentages can diverge, especially in obstructive disease where air trapping raises TLC and residual volume while FVC stays reduced.

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Age, Height & Sex

Predicted TLC

Percent Predicted Breakdown

Interpretation Bands

Reading Your Result

Why This Can't Replace a Real PFT

How to Use This Calculator

Enter age, height, and sex

Add a measured TLC if you have one

Check the validity range before relying on the result

Formula & Methodology

Trust, Methodology & Sources

Key Terms Explained

Real-World Examples

Healthy 28-year-old woman

Adult male with a PFT in hand

Patient with suspected pulmonary fibrosis

Understanding the Lung Capacity Calculator

How predicted TLC is calculated

Reading your percent predicted

Why this can't replace a real pulmonary function test

Frequently Asked Questions

Get a branded PDF of your results

🫁 Age, Height & Sex

📊 Predicted TLC

➗ Percent Predicted Breakdown

📈 Interpretation Bands

🩺 Reading Your Result

🛡️ Why This Can't Replace a Real PFT

How to Use This Calculator

Enter age, height, and sex

Add a measured TLC if you have one

Check the validity range before relying on the result

Formula & Methodology

Trust, Methodology & Sources

Key Terms Explained

Real-World Examples

Understanding the Lung Capacity Calculator

How predicted TLC is calculated

Reading your percent predicted

Why this can't replace a real pulmonary function test

Frequently Asked Questions

Get a branded PDF of your results

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