Lung Capacity Calculator

Written by Great Medico

Updated September 24, 2026 •2 min read

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A lung or oxygenation value can be easy to misread when the formula is hidden. Lung Capacity Calculator makes the calculation explicit, so you can see what the result represents—and what it does not.

What this calculator does

Lung Capacity Calculator uses Inspiratory reserve volume (IRV), Tidal volume (TV), Expiratory reserve volume (ERV), and Residual volume (RV) to produce the total lung capacity from entered volumes used by this calculator. It only uses the fields shown in this calculator; it does not silently add tests, diagnoses, symptoms, or clinical variables that are absent from the interface. Calculates TLC, vital capacity, inspiratory capacity and functional residual capacity from four lung-volume components.

How to use it

Enter or select Inspiratory reserve volume (IRV), Tidal volume (TV), Expiratory reserve volume (ERV), and Residual volume (RV). Use measurements from the same respiratory assessment and confirm whether oxygen values are percentages, fractions, or pressures. If an input is unknown, it is better to leave the calculation unresolved than to invent a value.

How the calculation works

The calculation is component arithmetic: total lung capacity = IRV + tidal volume + ERV + residual volume; vital capacity = IRV + tidal volume + ERV; inspiratory capacity = IRV + tidal volume; and functional residual capacity = ERV + residual volume.

Example

Using the calculator’s prefilled demonstration values, the primary output is 5.8 L, labeled “Total lung capacity from entered volumes”; Vital capacity (VC) is 4.6 L and Inspiratory capacity (IC) is 3.5 L. That sample is useful for checking the calculation path, but real interpretation should use verified measurements from the same clinical or study context.

How to interpret the result

Read total lung capacity from entered volumes in the context of the pulmonary measurement or scoring system used. Trends, measurement quality, oxygen/ventilator settings, and the disease being evaluated usually matter more than an isolated decimal value.

Limitations and notes

Respiratory measurements depend on technique, calibration, oxygen/ventilator settings, altitude, timing, and the patient population in which a rule was validated. A single calculated value should be interpreted with symptoms, examination, serial measurements, imaging, and the clinical question that prompted the test.