What Is Mean Arterial Pressure (MAP) and How Is It Calculated?

Mean arterial pressure (MAP) is the average pressure in your arteries across one full heartbeat. It's usually estimated as your diastolic number plus one third of the gap between your two numbers, so a reading of 120/80 mmHg gives a MAP of about 93. It's a calculation used mostly in hospitals, not a separate category for home readings.

The short version, with the numbers

The NIH's StatPearls reference (DeMers and Wachs) defines MAP as the average arterial pressure through one cardiac cycle, systole and diastole together, and gives the common bedside estimate: MAP = diastolic + ⅓ × (systolic − diastolic). The result sits closer to the bottom number because each heartbeat spends longer relaxing than contracting. MAP depends on how much blood the heart pumps and how much the vessels resist that flow. In intensive care it matters a great deal: the 2021 Surviving Sepsis Campaign guideline recommends an initial target MAP of 65 mmHg for adults in septic shock. For home readings, though, the AHA, ESH and NICE all classify blood pressure by systolic and diastolic. None of them sets a MAP cutoff.

BPlus color-codes every reading into the same five ranges. Check my readings →

How do you calculate mean arterial pressure?

You need only the two numbers from a normal reading. Subtract the bottom number from the top one (that gap is your pulse pressure), take a third of it, and add the result back to the bottom number.

Take 130/80 as an example:

1. Gap: 130 − 80 = 50
2. One third of the gap: 50 ÷ 3 ≈ 17
3. Add it to the diastolic: 80 + 17 = 97 mmHg

Some people write the same thing as (systolic + 2 × diastolic) ÷ 3. It's identical arithmetic, just arranged differently.

Treat the last column as a rough figure. The one-third rule is a shortcut. In a study by Vos and colleagues, MAP measured from the pulse wave sat at about 38% of the gap above diastolic, not exactly 33%. The real share also shifts from person to person.

Two very different readings, the same MAP

Because MAP squeezes two numbers into one, it can hide exactly what a clinician would want to see.

Both work out to a MAP of 100. But the first has a high systolic and a wide gap, the pattern often seen in isolated systolic hypertension, where stiffer arteries push the top number up. The second has a raised diastolic and an ordinary gap. Those are different situations, and the averaged figure can't tell them apart.

That's why home blood pressure guidelines ask for both numbers. Under the ACC/AHA guideline, used in the US, high blood pressure starts at 130/80 mmHg. The ESH and NICE, followed across Europe and the UK, set the clinic line at 140/90. Each of these is a pair of numbers, and none of them is a MAP value.

Your home monitor finds MAP first

The automatic cuff on your table probably works out MAP before anything else. As the cuff deflates, it senses small pressure pulses in the artery. A 2025 study in Hypertension Research by Picone and colleagues describes recording this oscillometric MAP as a key step in automated devices. The systolic and diastolic numbers on the screen are then estimated from it with each maker's own algorithm.

So why don't most monitors show MAP? One reason is accuracy. In the Vos study, an office oscillometric monitor's MAP averaged 97 mmHg, against 106 mmHg from pulse wave analysis in the same 102 people. The authors suggested devices shouldn't display MAP unless that figure has been tested for accuracy. The monitor in that study had been validated for its systolic and diastolic readings, which is the pair your doctor reads.

If your monitor does show a MAP figure, it's fine to note it. Just don't treat it as more precise than the two numbers it came from. If you're not sure what each part of your screen means, our guide on how to read a blood pressure monitor display goes through the labels and icons.

When a reading needs action, not math

MAP doesn't change what to do with a very high reading. The American Heart Association calls a reading above 180/120 mmHg (either number) a hypertensive crisis. If you have chest pain, shortness of breath, back pain, numbness or weakness, vision changes or trouble speaking, seek medical help immediately.

Without symptoms, the AHA advises waiting about 5 minutes and measuring once more. If the second reading is still above 180/120, seek medical help immediately. Don't keep re-measuring until a lower number appears.

The low end works the same way. Feeling faint, dizzy or confused alongside a low reading is a reason to contact a healthcare professional promptly, whatever the MAP works out to.

Keeping the numbers MAP is built from

Any MAP figure, yours or a clinician's, starts from systolic and diastolic. A clean record of those two numbers is the useful part.

BPlus lets you log systolic, diastolic and pulse by hand, or scan the display of your own monitor with the camera, with the time, date and arm stamped automatically. Readings are color-coded by the five widely used ranges, trends and charts show how your numbers move over weeks, and a doctor-ready PDF or CSV export gives your clinician the full history. BPlus doesn't measure blood pressure or work out MAP for you. It's a wellness and logging tool, not a medical device, and your data stays on your phone with no account needed.

Common questions about MAP

Is a MAP of 100 high? There's no home-reading cutoff for MAP, so the number alone doesn't answer it. A MAP of 100 can come from 150/75 or from 130/85, and those carry different meanings. Look at your systolic and diastolic against the guideline your clinician uses, and bring a few weeks of readings to your next appointment.

Is mean arterial pressure the same as average blood pressure? Not quite. MAP is the average pressure within a single heartbeat. An "average blood pressure" from home monitoring usually means the mean of several separate readings, each kept as a systolic and diastolic pair. Our post on how many readings to average covers that kind of average.

Why is MAP closer to the diastolic number? Each heartbeat spends more time in the relaxed phase (diastole) than in the pumping phase (systole). Pressure stays near the diastolic level for longer, so the time-weighted average lands below the midpoint. That's why the estimate adds only a third of the gap to the bottom number rather than half.

Sources

• NIH StatPearls: Physiology, Mean Arterial Pressure (DeMers and Wachs)
• Evans et al., 2021: Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021 (Intensive Care Medicine)
• Vos et al., 2013: Inaccuracy in determining mean arterial pressure with oscillometric blood pressure techniques (American Journal of Hypertension)
• American Heart Association: Understanding Blood Pressure Readings