Mean arterial pressure calculator
Mean arterial pressure calculator
Mean arterial pressure from a systolic and a diastolic reading, and the pulse pressure between them, with the approximation the formula makes stated beside it.
How this is calculated
Mean arterial pressure = (systolic + 2 × diastolic) ÷ 3. Pulse pressure = systolic - diastolic. The formula is an approximation that treats two-thirds of the cardiac cycle as diastole.
- The approximation assumes a normal heart rate and a normal arterial waveform. At a high heart rate the true mean sits closer to the systolic figure, and an arterial line measures the mean directly — where one is in place, its reading is the reference.
- A cuff reading is a measurement with its own error, and one reading is a point. Nothing here decides whether a pressure is adequate for an organ; that is a clinical judgement made with the whole picture.
- This page does the arithmetic and prints the unit beside every answer. It has no patient in front of it: it does not diagnose, does not choose or change a treatment, and does not replace the prescription, protocol or formulary you are working under. It has not been reviewed by a clinician for use in care, so treat it as a check on your own working — confirm the figure with an independent calculation and a qualified clinician before it is acted on.
Mean arterial pressure from a systolic and a diastolic reading, and the pulse pressure between them, with the approximation the formula makes stated beside the answer.
An estimate from a cuff, not a measurement of the mean
The formula adds the systolic pressure to twice the diastolic and divides by three. It is an approximation that treats roughly two-thirds of the cardiac cycle as diastole, and it holds best when the heart rate and the arterial waveform are close to normal. At a high heart rate the true mean sits nearer the systolic figure, and the estimate drifts.
Where an arterial line is in place it measures the mean directly, and its reading is the reference. The page prints the pulse pressure as well because the difference between the two cuff numbers is often as informative as the mean, and because having both makes the arithmetic visible.
Questions readers ask
Why does it say the systolic must be higher?
Because a reading with the numbers the other way round is usually a transcription error, and the formula would still return a number. The page refuses to compute it and asks for the reading to be checked instead.
Is the mean used to set treatment?
Not by this page. It computes an estimate and prints its assumptions. Any decision about treatment belongs to the clinician, with the whole picture and the monitoring in place.
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