Mean Arterial Pressure

Because diastole lasts about twice as long as systole at a resting heart rate. The cardiac cycle at 60–70 beats per minute spends roughly one-third of its time in systole and two-thirds in diastole. MAP is a time-weighted average, so the diastolic value counts twice as heavily as the systolic value. This is why the formula divides the pulse pressure (SBP − DBP) by 3 rather than by 2. If diastole and systole were equal in duration, MAP would be (SBP + DBP)/2; at a resting heart rate, the true time-weighted mean sits roughly one-third of the way from DBP up to SBP, which pulls MAP well below the arithmetic midpoint. At very high heart rates the ratio changes, but the /3 approximation remains clinically useful.

For a healthy resting adult with a blood pressure of 120/80, MAP is about 93 mmHg. The generally accepted normal range is roughly 70–100 mmHg. Below 70, and especially below 60, the perfusion pressure starts to be inadequate for the brain, kidneys, and coronary circulation — this is the range of clinical hypotension. Above 100 is considered elevated, and above 110 significantly so. In the ICU, the standard target is MAP ≥ 65 mmHg for most patients, though this shifts upward for patients with chronic hypertension (whose autoregulation curve is shifted to the right) and downward in some specific circumstances such as post-cardiac-arrest cooling. Your personal target depends on your age, medical history, and clinical condition — discuss it with your healthcare provider.

Pulse pressure is the difference between systolic and diastolic pressure: PP = SBP − DBP. A normal pulse pressure is 30–50 mmHg. It carries information that MAP does not: two patients with identical MAPs can have very different pulse pressures, and the pulse pressure is often the more revealing number. A wide pulse pressure (over 60 mmHg) usually indicates arterial stiffness, which is common with aging and atherosclerosis, and it is associated with increased cardiovascular risk. It can also reflect increased stroke volume (as in aortic regurgitation, hyperthyroidism, or anaemia) or reduced diastolic runoff (as in patent ductus arteriosus). A narrow pulse pressure (under 25 mmHg) usually indicates reduced stroke volume, as in heart failure, hypovolaemia, cardiac tamponade, or aortic stenosis. Pulse pressure is therefore an important independent parameter alongside MAP and the individual pressures.

No — both the actual MAP and the appropriate target MAP vary substantially by age, sex, pregnancy, and clinical condition. A healthy young athlete might run a MAP of 85 and feel perfectly well, while an older adult with chronic hypertension might need a MAP of 100 or more to perfuse their brain because their autoregulation curve has shifted to the right over decades of high pressure. In pregnancy, MAP falls slightly in the second trimester and rises back in the third; a MAP ≥ 90 in mid-pregnancy is a risk marker for preeclampsia. In infants and children, target MAPs are age-specific, rising from about 50 mmHg in newborns to 65–75 in adolescents. And in a patient on chronic antihypertensive medication, the "normal" MAP range may not apply — the target is whatever keeps the patient symptom-free and perfusing adequately, which is often higher than textbook values.

In routine office practice, clinicians usually focus on systolic and diastolic pressures because those are the numbers printed on the blood pressure cuff, and the AHA classification is defined in terms of them. MAP becomes the primary target in two situations: critical care (where an arterial line gives a continuous MAP reading and haemodynamic therapy is titrated to a MAP target), and general haemodynamic reasoning (where the effect of a drug or manoeuvre on tissue perfusion is estimated from the MAP change). When systolic and diastolic pressures disagree — for example, isolated systolic hypertension with a normal diastolic in an older adult — MAP helps to reconcile them and gives a single number to track. And when pulse pressure is unusually wide or narrow, both the MAP and the pulse pressure should be reported, because they carry independent information.

No. This calculator performs the arithmetic of the MAP formula, and it can help you understand what the numbers mean, but it cannot diagnose hypertension, prescribe treatment, or replace a clinical assessment. A hypertension diagnosis requires multiple blood pressure readings on separate occasions, using a properly sized cuff and correct technique, ideally combined with home or ambulatory monitoring. Clinical decisions about medication, target blood pressures, and treatment strategy depend on the whole clinical picture — age, sex, cardiovascular risk factors, kidney function, pregnancy status, other medications, and symptoms. If you are concerned about your blood pressure, please measure it properly and discuss the readings with a qualified healthcare provider.

The formula MAP = DBP + (SBP − DBP)/3 is a mathematical identity that applies to any pressure pair, so the arithmetic works fine in children. However, the interpretation is completely different. Paediatric blood pressure targets are age-specific and rise steadily from infancy: a newborn might have a target MAP of 40–50 mmHg, a young child 50–60, an older child 60–70, and an adolescent approaching adult values of 65–75. The MAP formula also becomes slightly less accurate at very high heart rates, which are normal in infants and young children, because the time-weighting assumption of ⅓ systole no longer holds as well. Paediatric MAP values should always be interpreted against age-specific reference ranges, not adult thresholds.