To calculate average blood pressure, add up all the systolic (top) numbers and divide by the number of readings, then do the same, separately, for the diastolic (bottom) numbers, and write the result as a pair such as 126.7/81.0. Never average the top and bottom numbers together. NICE guideline NG136 (2019) asks for two seated readings, morning and evening, for at least four days and ideally seven, then discards the first day and averages everything that remains, which leaves 24 readings from a full week (two readings, twice a day, for six days).
How do I calculate my average blood pressure?
To calculate an average blood pressure, add up the systolic (top) numbers of every reading that counts and divide by how many readings there are, then do the same for the diastolic (bottom) numbers. Write the result as systolic over diastolic. For example, 24 home readings whose systolic values total 3,040 and whose diastolic values total 1,944 average 126.7/81.0 mmHg.
- Decide which readings count before looking at the numbers. The usual home schedule is in how many blood pressure readings a day.
- Put the systolic numbers in one column and the diastolic numbers in another, one reading per row.
- Add up the systolic column and divide by the number of readings (readings, not days).
- Do the same for the diastolic column, using exactly the same readings.
- Write the pair down with its dates and reading count, and keep the raw readings so the sums can be checked.
Here is an example week in the NICE pattern, with two readings each morning and evening. The numbers are invented for illustration.
| Day | Morning (2 readings) | Evening (2 readings) | Day average |
|---|---|---|---|
| Day 1, not counted | |||
| Day 2 | 131/84, 128/82 | 127/82, 126/80 | 128/82 |
| Day 3 | 128/82, 124/80 | 125/80, 123/78 | 125/80 |
| Day 4 | 133/86, 130/85 | 129/83, 128/82 | 130/84 |
| Day 5 | 126/81, 123/79 | 124/79, 123/77 | 124/79 |
| Day 6 | 130/83, 126/81 | 127/81, 125/79 | 127/81 |
| Day 7 | 128/82, 125/80 | 126/80, 125/78 | 126/80 |
| Days 2–7, 24 readings | 126.7/81.0 |
Systolic: 3,040 ÷ 24 = 126.7. Diastolic: 1,944 ÷ 24 = 81.0. Averaging the six day averages gives the same answer only because every day has four readings; if a session is missed, average the individual readings so a short day does not count as much as a full one.
Do I average systolic and diastolic separately?
Yes. Average the systolic readings on their own and the diastolic readings on their own, then report the result as a pair. NICE and the 2024 European Society of Cardiology guidelines both write their home threshold for diagnosing hypertension that way, as 135/85 mmHg. Adding each top and bottom number together and halving the total turns an example average of 126.7/81.0 into a single figure, 103.8, that no guideline uses.
| Method | Result for the example week | What it is |
|---|---|---|
| Systolic and diastolic separately, days 2–7 | 126.7/81.0 | The NICE NG136 home average |
| Systolic and diastolic separately, all 7 days | 128.4/82.0 | The ESC 2024 approach, which keeps day one |
| (Systolic + diastolic) ÷ 2 | 103.8 | A mistake: one number that means nothing |
| Diastolic + (systolic − diastolic) ÷ 3 | About 96 | Mean arterial pressure, a different measure |
Which readings go into a weekly average?
Which readings count depends on the protocol, and protocols differ. NICE guideline NG136 discards the first day of home readings, while the 2024 European Society of Cardiology guidelines average every reading from at least three and up to seven days. NICE and the ESC use both readings from each sitting, while some hospital guides, such as Rabin Medical Center's in Israel (in Hebrew), record only the last. Note which rule was used beside the average.
For clinic readings, the ESC averages the last two of three, whereas NICE takes a second reading only if the first is 140/90 mmHg or higher, adds a third only if the second differs substantially from the first, and records the lower of the last two. Use the rule you were given, every time, and note which it was.
How do I calculate the average in Excel or Google Sheets?
In Excel or Google Sheets, put =AVERAGE(C6:C29) in cell C31, under the systolic column, and =AVERAGE(D6:D29) in D31, under the diastolic column, covering only the rows that count. Then work out MAP as =D31+(C31-D31)/3 and pulse pressure as =C31-D31 from those two averages. Leave a missed reading blank, never 0: in a worked example week, typing 0 for one missed reading turns a 126.8 systolic average into 121.5.
| What you want | Formula (day one in rows 2–5, days 2–7 in rows 6–29, averages in row 31) |
|---|---|
| Mean arterial pressure (MAP) | =D31+(C31-D31)/3 |
| Pulse pressure | =C31-D31 |
With headers in row 1, those ranges cover the 24 readings from days 2 to 7. In the example week, leaving day 5's second evening reading (123/77) blank gives 126.8/81.2 from 23 readings. Type 0 into both of its cells instead and Excel's AVERAGE divides by 24, giving 121.5/77.8: more than 5 mmHg off on systolic from a single missed reading. In Google Sheets, use AVERAGE rather than AVERAGEA, which Google's help page says counts text as zero, so a cell with "missed" typed in it would be averaged as a 0 reading. Helper columns, AVERAGEIFS for morning and evening averages, and a chart are in how to make a blood pressure log in Excel or Google Sheets.
What is mean arterial pressure (MAP) and how is it calculated?
Mean arterial pressure (MAP) is the average pressure in the arteries across one full heartbeat. The common estimate, given in StatPearls on the NCBI Bookshelf, is MAP = diastolic + (systolic − diastolic) ÷ 3, so a reading of 120/80 gives 80 + 40 ÷ 3, about 93 mmHg. MAP is a different measure from the average of several readings.
| Reading | Working | MAP |
|---|---|---|
| 120/80 | 80 + (120 − 80) ÷ 3 = 80 + 13.3 | About 93 mmHg |
| 126.7/81.0 (example week average) | 81.0 + (126.7 − 81.0) ÷ 3 = 81.0 + 15.2 | About 96 mmHg |
Because the StatPearls formula is linear, working out MAP for each reading and averaging gives the same result as working it out once from the weekly averages: about 96 for the example week.
Treat the result as an estimate. When Meaney and colleagues checked the one-third rule in 2000 against catheter-measured pressure in 150 patients having cardiac catheterisation, it underestimated the true mean, more so as the gap between the two numbers widened. Automatic monitors do not usually rely on this formula. A 2023 review in the Journal of Human Hypertension explains that oscillometric monitors typically estimate MAP at the point where the cuff's pulsations are strongest, work out systolic and diastolic with each maker's own unpublished algorithm, and only occasionally display MAP. A MAP shown on a monitor may therefore not match your hand calculation. What a particular MAP means for you is a question for your clinician.
What is pulse pressure and how is it calculated?
Pulse pressure is systolic minus diastolic, the gap between the two numbers of a blood pressure reading. A reading of 120/80 has a pulse pressure of 40 mmHg, and a weekly average of 126.7/81.0 gives about 46 mmHg. It is calculated from the reading rather than measured on its own, and it is not pulse rate, the heartbeats-per-minute figure a monitor may show.
The definition is from StatPearls (2023), and because subtraction is linear, the order of working does not matter here either. What a particular pulse pressure means for you is a question for your clinician. The heartbeats-per-minute figure a monitor shows, and why it is a different measure, is covered in pulse rate on a blood pressure monitor.
What should I do with my average blood pressure?
Take the average to your clinician with the dates, the number of readings and the raw readings behind it. NICE and the 2024 European Society of Cardiology guidelines both use a home average of 135/85 mmHg, not the clinic figure of 140/90 mmHg, as the threshold for diagnosing hypertension. Which threshold applies to you, and what your number means, is for your clinician to say.
Home readings usually run lower than clinic readings, which is why the home threshold is set lower: NICE NG136 puts home figures 5 mmHg below the matching clinic ones. A week of home readings can also show patterns that a single appointment misses, as described in why blood pressure is higher at the doctor's than at home. An average is only as good as its readings: the 2024 ESC guidelines ask patients to have their monitor's accuracy checked from time to time and note that devices older than four years may be inaccurate.
On paper, the NHS-style seven-day printable diary has slots for two readings each morning and evening (our layout, not an NHS document), and the division is yours. In the Monitor2Log diary, the print report's "Average for each measurement column" option averages each column separately. It uses only the rows in your chosen date range or the rows you tick, so day one can be left out. It shows whole numbers, so the example week prints as 127/81.
Sources
- European Society of Cardiology, 2024, hypertension guidelines: home and clinic measurement, home thresholds and device accuracy.
- NICE, 2019 (last updated 2026), guideline NG136: the home monitoring schedule, discarding day one, clinic readings and the 135/85 home average.
- StatPearls, NCBI Bookshelf, 2023, Physiology, Mean Arterial Pressure, with Physiology, Pulse Pressure: the definitions and the one-third formula.
- Heart, 2000, Meaney and colleagues comparing the one-third formula with catheter-measured mean pressure.
- Journal of Human Hypertension, 2023, Sharman and colleagues on how automated oscillometric monitors work.
- Microsoft Support, 2026, the Excel AVERAGE function and how it treats blank cells and zeros, with Google Docs Editors Help on AVERAGE and AVERAGEA in Google Sheets.
General information only, not medical advice. Which readings to count, which threshold applies and what your average means are decisions for your own clinician.