Free · Pulmonary calculators 💨

Lung Volume and Capacity Sums

Combine measured component lung volumes into the standard capacity sums.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Health results are educational estimates, not a diagnosis or treatment recommendation. A qualified clinician can interpret measurements in the context of your health.

Formula and method

IRV 3 L, tidal volume 0.5 L, ERV 1 L and residual volume 1.5 L give TLC 6 L, VC 4.5 L, FRC 2.5 L and IC 3.5 L.

TLC = IRV + TV + ERV + RV; VC = IRV + TV + ERV; FRC = ERV + RV; IC = IRV + TV.

Worked example

Enter these known values and leave the other values blank.

Inspiratory reserve volume (IRV)
3 L
Tidal volume (TV)
0.5 L
Expiratory reserve volume (ERV)
1 L
Residual volume (RV)
1.5 L
Total lung capacity (TLC)
6 L
Vital capacity (VC)
4.5 L
Functional residual capacity (FRC)
2.5 L
Inspiratory capacity (IC)
3.5 L

Assumptions and limitations

  • Nonnegative component volumes are combined in matching volume units. These identities do not predict normal capacity for a person. Residual volume cannot be measured by simple spirometry alone.
  • Use the displayed units and measurements from the same context. Editable fields support arithmetic inverses when enough independent values are supplied. Clear a preset value before solving it as an unknown.
  • This tool performs the stated arithmetic model. It does not establish a diagnosis, prescribe treatment or replace laboratory and clinical assessment.

Common questions

What does this calculation represent?

Nonnegative component volumes are combined in matching volume units. These identities do not predict normal capacity for a person. Residual volume cannot be measured by simple spirometry alone.

Can I solve for a different field?

Clear the unknown field and enter enough independent values in the remaining editable controls. A relationship cannot recover a unique value when a dividing quantity is zero.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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