Peak Flow Calculator – Estimated Peak Expiratory Flow

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. Peak Flow Calculator – Estimated Peak Expiratory Flow makes the calculation explicit, so you can see what the result represents—and what it does not.

What this calculator does

Peak Flow Calculator – Estimated Peak Expiratory Flow uses Sex, Age, Height, Ethnicity, Measured PEF, Personal best, and the remaining displayed fields to produce the estimated pef 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. Mirrors patient-details, measured PEF, personal-best, and diurnal-variability sections.

How to use it

Enter or select Sex, Age, Height, Ethnicity, Measured PEF, and the remaining displayed fields. 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 primary estimate uses sex-, age-, and height-based peak-expiratory-flow reference equations. The calculator also accepts measured PEF, personal best, and maximum/minimum PEF so it can display comparisons and variability when those fields are supplied.

Example

Using the calculator’s prefilled demonstration values, the primary output is 524 L/min, labeled “Estimated PEF”; Measured PEF is 500 L/min and Measured / estimated is 95.3%. 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 estimated pef 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

Predicted PEF equations vary by population, sex definition, ethnicity/reference set, device, and technique. Asthma action plans usually emphasize a person’s reproducible personal best and symptoms rather than a single population-predicted value.