Mean Arterial Pressure Calculator

Mean arterial pressure (MAP) is the time-weighted average of arterial pressure across a single cardiac cycle, not the arithmetic average of systolic and diastolic. Diastole occupies roughly two-thirds of the cycle at a resting heart rate of 60 to 80 bpm and systole roughly one-third, so the curve sits closer to the diastolic value for longer. That is why the standard estimate weights diastole twice: MAP = (2 x DBP + SBP) / 3. Physiologically, MAP is the driving pressure that pushes blood through the systemic circulation past the precapillary sphincters, so it is the variable that matters for end-organ perfusion in shock, anesthesia, and critical care.

The Surviving Sepsis Campaign 2021 international guidelines recommend an initial MAP target of at least 65 mmHg for adults with septic shock on vasopressors. Below 65 mmHg, 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, lactate accumulation, and in-hospital mortality. The same 65 mmHg target is the standard intraoperative trigger for vasopressor support in most anesthesia protocols. It is a population-level safety threshold, not a personal target: patients with chronic hypertension often need a higher MAP for adequate perfusion, and a clinician sets the individual goal.

The standard MAP estimate MAP = (2 x DBP + SBP) / 3 assumes the cardiac cycle spends two-thirds of its time in diastole and one-third in systole. That ratio holds at resting heart rates roughly 60 to 80 bpm, but diastole shortens disproportionately as heart rate rises. Razminia and colleagues (American Journal of Hypertension, 2004) showed that MAP = DBP + 0.4 x (SBP - DBP) tracks invasive arterial measurements better when heart rate exceeds about 100 bpm. The auto setting in this calculator switches to Razminia only when a heart rate is provided and strictly above 100 bpm; at rest the difference is small and the standard formula is the safer default.

Pulse pressure is systolic minus diastolic pressure and provides different information from the estimated mean. A persistent wide or narrow value can have several causes, but a calculator cannot distinguish arterial stiffness, measurement error, medication effects, valve disease, or low stroke volume. Repeat an unexpected reading correctly and seek clinical assessment when it persists or occurs with concerning symptoms.

Call emergency services for any reading over 180/120 mmHg paired with chest pain, shortness of breath, weakness on one side, vision change, severe headache, or confusion. Those are signs of a hypertensive emergency with end-organ damage. A reading over 180/120 mmHg without symptoms (hypertensive urgency) still warrants prompt medical contact, ideally within hours. A MAP under 65 mmHg, especially with cool extremities, low urine output, dizziness on standing, or confusion, is a sign of inadequate perfusion and needs urgent evaluation. For everything else, the 2017 ACC/AHA guideline calls for an average of two or more readings on two or more occasions before any diagnosis or medication change. A single in-office number is rarely enough on its own.