Mean Arterial Pressure (MAP) Calculator
Mean arterial pressure estimates the average pressure in your arteries across a heartbeat. It is a useful single number for organ perfusion.
| Result | Interpretation |
|---|---|
| Below 60 mmHg | Low |
| 60 mmHg to 70 mmHg | Low-normal |
| 70 mmHg to 100 mmHg | Normal |
| 100 mmHg and above | Elevated |
Source: Standard mean arterial pressure estimate: MAP = (SBP + 2 x DBP) / 3. Sainas G, et al. (review of MAP estimation).
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How to calculate mean arterial pressure
The standard formula is:
MAP = (SBP + 2 × DBP) / 3
which is the same as writing MAP = DBP + 1/3 × (SBP − DBP).
Diastole is weighted twice as heavily as systole because at a normal resting heart rate your heart spends roughly twice as long relaxing as it does contracting. MAP is a time weighted average, not a simple midpoint between the two numbers.
Worked example
For a blood pressure of 120/80:
- Pulse pressure = 120 − 80 = 40 mmHg
- MAP = 80 + (40 / 3) = 80 + 13.3 = 93 mmHg
Using the other form: (120 + 160) / 3 = 280 / 3 = 93 mmHg. Same answer.
What counts as a normal MAP
| MAP | Interpretation |
|---|---|
| Below 60 mmHg | Perfusion of the brain, kidneys, and other organs is likely inadequate |
| 60 to 70 mmHg | Marginal, the usual resuscitation floor in critical care |
| 70 to 100 mmHg | Normal range for a healthy adult |
| Above 100 mmHg | Consistent with hypertension, worth evaluating |
A MAP near 93 mmHg, as in the example above, is exactly what you would expect from a textbook normal blood pressure.
Why MAP matters more than either number alone
Blood flow to an organ depends on the pressure driving it, averaged across the whole cardiac cycle. That average is MAP. Systolic pressure tells you about the peak load on your arteries and correlates well with stroke risk. Diastolic pressure tells you about the resting tone of your vasculature. Neither one on its own tells you whether an organ is being adequately perfused.
This is why critical care runs on MAP rather than systolic pressure. The Surviving Sepsis Campaign targets a MAP of at least 65 mmHg in septic shock, because below roughly that threshold the kidneys and other organs begin to fail regardless of what the systolic number looks like.
In my own field the relationship is even more direct. Cerebral perfusion pressure, the pressure actually driving blood into the brain, is MAP minus intracranial pressure:
CPP = MAP − ICP
If someone has a raised intracranial pressure after a head injury, a MAP that would be perfectly acceptable in a healthy person can leave the brain underperfused. That is the entire reason we manage blood pressure so carefully in neurosurgical patients rather than just treating a number.
Where the formula breaks down
The one third weighting assumes a normal resting heart rate, roughly 60 to 100 beats per minute. At higher heart rates diastole shortens far more than systole does, so the true average shifts upward and this formula underestimates MAP. During significant tachycardia the real MAP moves closer to the arithmetic mean of the two pressures.
Two other limits worth knowing:
- It is only as good as your blood pressure reading. A cuff that is too small, an unsupported arm, or a reading taken right after walking in will all distort the result more than any formula subtlety.
- In an intensive care setting, MAP is measured directly. An arterial line integrates the actual pressure waveform rather than estimating from two numbers, which is why the displayed MAP on a monitor may differ slightly from what this calculator returns.
Pulse pressure is worth a look too
While you have both numbers in front of you, subtract them. Pulse pressure (systolic minus diastolic) normally runs about 40 mmHg. A persistently wide pulse pressure, above roughly 60 mmHg, tends to reflect arterial stiffening and is itself associated with cardiovascular risk in older adults. A very narrow one can appear in low output states.
FAQs
What is mean arterial pressure?
Mean arterial pressure is the average pressure in your arteries across one full cardiac cycle. It matters because it is the pressure that actually drives blood into your organs, which is why clinicians use it as the target when perfusion is in question.
What is a normal MAP?
Roughly 70 to 100 mmHg in a healthy adult. Below about 60 mmHg organs may not be adequately perfused. Persistently above 100 mmHg is consistent with hypertension and worth discussing with your physician.
Why is diastolic pressure weighted twice in the formula?
Because at a normal heart rate the heart spends about two thirds of each cycle in diastole and one third in systole. MAP is a time weighted average, so the phase that lasts longer contributes more.
Is MAP a substitute for a blood pressure reading?
No. MAP is calculated from a blood pressure reading you already have, so it adds interpretation rather than replacing measurement. Use an accurate, properly measured systolic and diastolic value or the result will not mean much.
What MAP is too low?
Below 60 mmHg is generally considered inadequate for organ perfusion, and 65 mmHg is the usual resuscitation target in septic shock. A single low reading in someone who feels well is far less concerning than a sustained low MAP with symptoms such as confusion, reduced urine output, or lightheadedness.
Does a normal MAP mean my blood pressure is fine?
Not necessarily. MAP can land in the normal range while the individual numbers are not, for example with a wide pulse pressure from a high systolic and a low diastolic. Look at systolic, diastolic, and MAP together rather than any one alone.