What this calculator does
Mean arterial pressure is the average pressure pushing blood through the circulation across a full heartbeat. It is not the midpoint of the systolic and diastolic figures, because the heart spends roughly twice as long relaxed as contracting.
That weighting is why a 120 over 80 reading gives 93.3 mmHg rather than 100. The diastolic figure carries two thirds of the weight, which is also why it matters more for organ perfusion than the headline systolic number.
The formula
Add one third of the difference between systolic and diastolic to the diastolic value. The weighting reflects the proportion of each cardiac cycle spent in diastole.
| Term | Meaning |
|---|---|
| MAP | Mean arterial pressure, the time-weighted average over one cardiac cycle. |
| Pulse pressure | The difference between systolic and diastolic, which the formula divides by three. |
| Perfusion | Blood flow to organs, which depends on mean pressure rather than peak pressure. |
The inputs explained
| Field | What to enter |
|---|---|
| Systolic blood pressure (mmHg) | Systolic blood pressure in mmHg, the upper figure. |
| Diastolic blood pressure (mmHg) | Diastolic blood pressure in mmHg, the lower figure. |
When to use it
Assessing organ perfusion
Mean pressure, not systolic, is what determines flow to the kidneys and brain.
Understanding a critical care target
Intensive care commonly targets a MAP threshold rather than a systolic one.
Reading your own measurements
MAP gives a single figure that summarises both numbers from a home monitor.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What does each reading give?
Systolic and diastolic pairs across a range.
| Systolic (diastolic 80) | Mean arterial pressure | Reference range |
|---|---|---|
| 100/80 mmHg | 86.7 mmHg | 70 - 100 mmHg |
| 120/80 mmHg | 93.3 mmHg | 70 - 100 mmHg |
| 140/80 mmHg | 100.0 mmHg | 70 - 100 mmHg |
| 160/80 mmHg | 106.7 mmHg | 70 - 100 mmHg |
Questions
Why is it not the simple average?
Because the heart spends about a third of each cycle contracting and two thirds relaxed. A simple average would weight the brief systolic peak equally with the much longer diastolic period, overstating the true mean.
What is a normal MAP?
Roughly 70 to 100 mmHg is the commonly cited range. Below about 60 is generally considered insufficient for organ perfusion, which is why critical care often uses 65 mmHg as a treatment target.
Is the formula exact?
It is an approximation that works well at normal heart rates. At high heart rates diastole shortens proportionally more than systole, so the one-third weighting becomes less accurate.
Should I act on a reading at home?
Not on a single reading. Blood pressure varies through the day and with activity, posture and stress. Persistent readings outside the usual range are worth taking to a clinician along with the record.
For the heart-rate-corrected ECG interval, see the QTc calculator. For cardiovascular risk from a lipid panel, see the cholesterol ratio calculator.