## Logic Behind Mean Arterial Pressure Formula & How to Calculate MAP WITHOUT Memorizing the Formula.

**Mean arterial pressure (MAP)** is a function of systolic and diastolic blood pressure.

The easiest way to calculate MAP is to get the pulse pressure (Systolic BP – Diastolic BP), then multiply the result with 1/3. The answer you get, add it to diastolic pressure and the result is the MAP.

1/3(SBP-DBP)+DBP = MAP

**Explanation.**

Systole is the time when the ventricles are contracting and diastole is the relaxation time. In normal condition, the systole phase takes about half the time the diastole takes. In other words, diastole takes twice as longer as systole.

This explains why we cannot just add systolic blood pressure and diastolic blood pressure and divide it with 2. The time each takes is different. Instead, if we divided the time into equal parts, we would have 3 equal parts, where the systole takes 1/3 and diastole take 2/3 of total time.

To test if this is true, we can multiply systolic BP by 1/3 and diastolic BP by 2/3 and add the results together to come up with the mean arterial pressure.

Let’s use the real example using the known formula of 1/3(SBP-DBP)+DBP = MAP and control theoretical explanation and see if we will come up with the same results.

Let’s say a patient BP = 120/60. Pulse pressure (SBP-DBP) would be 120-60 = 60.

Mean Arterial Formula: 1/3(SBP-DBP)+DBP = MAP

1/3 X 60 = 20

Add the result above to DBP (60)

20+60 = **80**

Let’s now use the theoretical way of testing if the formula above gives a true picture of how the heart works in normal conditions.

Our sample BP is 120/60

We will multiple SBP X 1/3 AND DBP X 2/3 and then add the total. We should get the same results as above

1/3×120 = 40 + 2/3×60 = 40. 40+40 = **80**

🙂

Happy? Leave your comments/compliments

Lorae says

Cool, I knew the formula but this explains the theory behind it so clearly.

Greg says

Thank you Lorae for the compliments

RSM says

its gud

Greg says

Thank you

Dr Awais Ahmed says

its very nice way to clear the concept regarding mean arterial pressure but do any body know what is the mechanism of mean arterial pressure checking in the monitors used in critical care like philips or hewlett packard. please let me know how they calculate even with nibp cuff they give mean pressure.

Greg says

Thank you Dr Awais for your compliments. I definately will dig into the monitors but I bet they compute the Systolic Blood pressure and diastolic blood pressure and they calculate the MAP using mean aterial pressure formula we all know about. Not hard to do at all programmatically using a software

Dr Igwe says

Excellent explanation, will use it to explain this phenomenon to my class.

Greg says

Thank you Dr. Igwe. for your compliments

Joey Hung says

Does diastole always take twice the time as systole REGARDLESS of heart rate? MAP is calculated the same way in human and cat. In a cat with heart rate of 160 and pressure of 120/60 and a human with heart rate of 70 and pressure of 120/60, do they have the same MAP?

JBW says

According to the article and the information given that MAP is calculated the same way for both humans and cats, I would say both the human and the cat have the same MAP, as the heart rate is not figured into the equation. The next question would be, does a MAP of 80 have the same indications for a cat as it does for a human?

Greg says

I didn’t know that. Good to know

domz tolentino says

nice one……..

Greg says

Thank you for the compliments

Judy, RN says

Interesting site, I like it. I am a senior nurse that learned the formula as : systolic + diastolic x 2

—————————-

3

= mean arterial pressure

You did have good answer behind the formula, sometimes we as nurses are told to learn a formula, but do not receive the theory behind it. I makes so much sense to learn both at once.

Greg says

@July, my explanation kind of decodes the formula or MAP and explains how that formula was formulated. I hope you found it helpful

Bimu says

Within our respiratory therapy field, we use the formula (2xDBP) + SBP/ 3. And it gives you the same answer. For example: (60×2) + 120 / 3 = 240 / 3 = 80mmHg. The explanation to it is the same as one given above.

Keith says

so now that we have the MAP …what is the recommended range for male in 70s ?

Greg says

With the numbers above explained and how MAP is calculated, it is not so evidence based practice (EBP) to dictate a mean aterial pressure based on age. So many factors come to play and that is why we only deal with a minimum mean aterial pressure of 60mm/Hg.

Greg says

@Bimu, thank you for your input about MAP calculation formula. Please note that this explanation on how to calculate mean aterial pressure is only explaining how the MAP formula was derived at