The formula, and why the diastolic counts twice
SBP is your systolic (top) number, DBP the diastolic (bottom) number. The heart sits at the lower diastolic pressure for about two-thirds of every beat and at the systolic peak for only a third, so the average is weighted toward diastolic. An equivalent way to write it is DBP + ⅓ of the pulse pressure (SBP − DBP).
What the number means
| MAP | Category | What it signals |
|---|---|---|
| ≥100 mmHg | Elevated | Extra strain on heart and vessels over time |
| 70–100 mmHg | Normal | Adequate flow to organs in a healthy adult |
| 65–70 mmHg | Low, watch | Below optimal; the usual clinical floor is 65 |
| <60 mmHg | Critically low | Organs start to run short of blood; emergency |
The 65 mmHg threshold comes from critical-care practice: it is the minimum average pressure generally needed to perfuse the kidneys and brain. It is a floor, not a personal ideal — someone whose usual blood pressure is high may need a higher MAP.
MAP is not the same as your systolic or diastolic reading
- Systolic. The peak pressure as the heart contracts — the brief high point, present only about a third of each beat.
- Diastolic. The resting pressure between beats, held roughly two-thirds of the time, which is why it drives MAP.
- MAP. The weighted average of the two. A textbook 120/80 gives a MAP of 93 mmHg — the pressure organs actually feel.
Common questions
How do I work out MAP from a blood pressure reading?
Add the systolic to twice the diastolic, then divide by 3. For 120/80: 120 + 160 = 280, divided by 3 is 93 mmHg. The diastolic is weighted double because the heart spends about two-thirds of each beat relaxed.
What is a normal MAP?
Roughly 70 to 100 mmHg in a healthy adult at rest. Below about 65 mmHg the pressure may be too low to keep organs like the kidneys and brain properly supplied, which is why 65 is the usual target floor in intensive care.
Why does MAP matter more than systolic pressure?
Systolic is only the brief peak of each heartbeat. MAP is the steady, average pressure that actually pushes blood through your tissues for the whole cycle, so it is a better measure of whether organs are being perfused.
