Mean Arterial Pressure (MAP) Calculator

Mean arterial pressure is estimated as MAP = (2 x DBP + SBP) / 3, which can also be written as DBP + (SBP - DBP) / 3. The two-thirds weight on diastolic pressure is not arbitrary: at a resting heart rate of 60 to 80 bpm, the cardiac cycle spends roughly two-thirds of its time in diastole and only one-third in systole. Time-averaging the pressure curve therefore tilts the result toward DBP. At very high heart rates this assumption breaks down because diastole shortens faster than systole, which is why intra-arterial monitoring is preferred in critical care.

The Surviving Sepsis Campaign 2021 international guidelines recommend an initial MAP target of at least 65 mmHg in adults with septic shock requiring vasopressors. Below that pressure, autoregulation of perfusion to the brain, kidneys, and gut starts to fail, and observational data link sustained MAP under 65 to higher rates of acute kidney injury and in-hospital mortality. The 65 mmHg floor is a population-level safety threshold, not a personal target: patients with chronic hypertension may need a higher MAP for adequate organ perfusion, and a clinician should set the goal.

Pulse pressure (SBP minus DBP) reflects stroke volume and arterial stiffness. A wide pulse pressure above 60 mmHg in adults is a clinical red flag for aortic regurgitation, acute aortic dissection, severe atherosclerosis, hyperthyroidism, or a high-output state like arteriovenous fistula. A narrow pulse pressure below 25 mmHg points toward low stroke volume: cardiogenic shock, severe aortic stenosis, cardiac tamponade, tension pneumothorax, or significant hypovolemia. MAP can look adequate while pulse pressure is signaling a serious problem, so both numbers belong on the same screen.

The 2017 ACC/AHA hypertension guideline lowered the diagnostic threshold from 140/90 to 130/80. Normal is SBP below 120 and DBP below 80. Elevated is SBP 120 to 129 with DBP still below 80. Stage 1 hypertension is SBP 130 to 139 or DBP 80 to 89. Stage 2 hypertension is SBP at or above 140 or DBP at or above 90. Hypertensive crisis is SBP above 180 or DBP above 120. A single in-office reading is not enough to stage hypertension: the guideline calls for an average of at least two readings on at least two occasions, ideally backed up by home or 24-hour ambulatory monitoring.

A noninvasive oscillometric cuff infers MAP from a single inflation cycle and can be off by 5 to 15 mmHg in shock, severe vasoconstriction, atrial fibrillation, or extreme obesity. An arterial catheter (most often in the radial artery) measures the pressure waveform continuously, so it is preferred when MAP guides vasopressor titration (septic, cardiogenic, or hemorrhagic shock), during major surgery, in patients on mechanical ventilation with PEEP, or whenever cuff readings disagree with clinical signs of perfusion. Arterial lines also enable repeated blood gas sampling, which makes them a near-default in most ICUs.