Mean Arterial Pressure (MAP) & Pulse Pressure Calculator

Understanding the mean arterial pressure calculator — concept and principle

Mean arterial pressure (MAP) is the average pressure in the arteries over one heartbeat, and it is the pressure that drives blood into the organs. This calculator also gives the pulse pressure, the difference between the top and bottom numbers, and the shock index, heart rate divided by systolic pressure. These are used in emergency and intensive care to judge perfusion, set blood pressure targets and spot early shock.

Because the heart spends longer relaxing than squeezing, MAP is closer to the diastolic value: about 93 mmHg here.

How it is calculated

MAP ≈ DBP + (SBP − DBP) ÷ 3

Pulse pressure = SBP − DBP

Shock index = heart rate ÷ SBP

SBP = systolic and DBP = diastolic blood pressure, both in mmHg.
Heart rate in beats per minute.

The principle

Arterial pressure is not a simple average of systolic and diastolic, because at a resting heart rate the heart spends roughly one-third of each cycle in systole and two-thirds in diastole. Weighting the diastolic value twice and the systolic value once, which is what DBP + one-third of the pulse pressure does, approximates the true time-averaged pressure. At fast heart rates diastole shortens and the formula becomes less accurate. The shock index works because in early blood loss the heart rate often rises before systolic pressure falls.

Worked example

Pulse pressure = 120 − 80 = 40 mmHg.
One-third of 40 = 13.33.
MAP = 80 + 13.33 = 93.33, shown as 93 mmHg.
Shock index = 75 ÷ 120 = 0.625, shown as 0.63.

Each point is the calculator re-run with only “Diastolic (mmHg)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Diastolic (mmHg)	MAP
20	53
40	67
60	80
80	93
100	107
120	120
160	147

How to read the result

Where does your result fall?

A typical resting MAP in healthy adults is roughly 70–100 mmHg. In septic shock, international guidelines recommend an initial target MAP of 65 mmHg in patients needing vasopressors; persistently lower values risk poor organ perfusion. A pulse pressure around 40 mmHg is typical; a persistently wide pulse pressure, often over 60 mmHg in older adults, reflects stiff arteries. A shock index of about 0.5–0.7 is normal, while values above 0.9 suggest haemodynamic instability.

Common mistakes

Swapping systolic and diastolic values.
Relying on the one-third rule at very fast heart rates.
Treating a normal MAP as proof of good perfusion; lactate, urine output and mental state also matter.

Keep in mind: These numbers are not a diagnosis. Cuff readings can differ from invasive arterial lines, and targets vary with the patient. Anyone with dizziness, fainting or signs of shock needs urgent medical care.

Frequently asked questions

What is a dangerous MAP?

A MAP below about 65 mmHg is a common threshold of concern in critically ill patients.

Is a high MAP harmful?

A persistently high MAP reflects high blood pressure, which raises long-term cardiovascular risk.

Why is the shock index useful?

It can flag hidden blood loss or sepsis when blood pressure still looks normal.

Sources: Evans L et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Crit Care Med 2021.

Checked 8 Nov 2026. Published formulas cited on the page. For information only — not medical advice.

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