Calculate systolic and diastolic averages separately from the set of readings you intend to summarize. The arithmetic is simple; choosing and describing the set matters just as much.
State the start and end dates and any filters.
List the included readings and count them.
Add the systolic values and divide by that count.
Repeat separately for the diastolic values.
State any exclusions and keep the original entries available.
An illustrative report label is: “Arithmetic mean of __ completed readings across __ recorded days; missing days: __; exclusions: __.” Do not call this a clinical protocol average unless its selection matches that protocol. Never average the upper and lower numbers together.
For the selection of readings in a clinical assessment, see the ESH home-monitoring position paper, Box 15. Its protocol context matters: an ordinary arithmetic report is not automatically the requested clinical assessment.
Worked arithmetic example: systolic readings of 120, 126 and 123 sum to 369; 369 divided by 3 is 123 mm Hg. Calculate the corresponding diastolic mean separately. These invented numbers illustrate the calculation, not a target or diagnosis.
An average can hide missing days and differences in measurement frequency. It does not describe every individual result, establish a diagnosis or override instructions for an unusual reading.
A common mistake is comparing two averages built from different filters without stating the difference.
If one day has six measurements and another has two, a mean of all eight gives the first day more weight. An average of two daily averages weights the days equally. These calculations can produce different answers. Neither should be described simply as “the average” without stating what was included.
The same issue arises with morning and evening groups. A period with mostly morning observations cannot automatically be compared with one dominated by evening entries. Keep the number of readings and represented days with the result, and describe missing observations rather than filling them with an assumed value.
An arithmetic mean of systolic readings is not a median, a chart's visual grouping or mean arterial pressure. If a report includes several kinds of summary, read their labels. A device or app may display a convenient aggregate that does not implement the clinical protocol requested by your care team.
Here is an illustrative reporting note: “Arithmetic means from all completed entries in the selected dates; three days had no records.” If a professional requests exclusions or a different protocol, keep the original data and document the new selection. Do not remove outliers merely because they change the result. An average is a description of a chosen set, not a diagnosis, a measurement-quality certificate or permission to ignore an individual event.
Read the guidance and research behind this article.
Updated 2026-11-12
