A blood pressure reading such as 120/80 mmHg gives two numbers, but clinicians often need one number that tells them whether the organs are receiving enough pressure to stay perfused. That number is the mean arterial pressure, or MAP. In this guide you will learn the MAP formula, normal values, worked examples, and why a MAP of 65 mmHg matters so much in sepsis and shock.
What Is Mean Arterial Pressure (MAP)?
Mean arterial pressure is the average pressure in the arteries across one full cardiac cycle, including both systole and diastole. It is a better indicator of tissue perfusion than systolic pressure alone, because organs receive blood during the entire heartbeat and not only at the peak.
Mean Arterial Pressure Formula
The most commonly used bedside formula is:
MAP = DBP + ⅓ (SBP − DBP)
This is the same as:
MAP = (SBP + 2 × DBP) ÷ 3
Why is diastolic pressure counted twice? In a normal resting heartbeat, the heart spends roughly two-thirds of the cycle in diastole and only one-third in systole, so the average pressure sits closer to the diastolic value than to the systolic one.
Related reading: the modified shock index uses MAP in place of systolic pressure. See our guide on the shock index formula.
How to Calculate MAP Step by Step
- Note the systolic blood pressure (SBP).
- Note the diastolic blood pressure (DBP).
- Subtract DBP from SBP to get the pulse pressure.
- Divide the pulse pressure by 3.
- Add the result to the diastolic pressure.
Worked Examples
Example 1: Normal blood pressure, 120/80 mmHg. Pulse pressure = 120 − 80 = 40. One-third of 40 = 13.3. MAP = 80 + 13.3 = 93.3 mmHg. This is within the normal range.
Example 2: Mildly raised, 130/85 mmHg. Pulse pressure = 45. One-third = 15. MAP = 85 + 15 = 100 mmHg, at the upper end of normal.
Example 3: Low blood pressure, 90/50 mmHg. Pulse pressure = 40. One-third = 13.3. MAP = 50 + 13.3 = 63.3 mmHg. This is below the 65 mmHg threshold and needs clinical attention, especially if the patient is septic or unwell.
You can also verify your calculation with an online MAP calculator.
Normal MAP Range
According to StatPearls, the normal range of MAP is 70 to 100 mmHg.
| MAP (mmHg) | Interpretation |
|---|---|
| Below 60 | Critically low, high risk of organ hypoperfusion |
| 60 to 65 | Low, at or just below the minimum treatment target in shock |
| 70 to 100 | Normal for most adults |
| Above 100 | Raised, consider causes such as hypertension |
These bands are a teaching guide. Treatment decisions depend on the patient’s baseline and clinical condition.
The Link Between MAP, Cardiac Output and Resistance
StatPearls describes MAP as the product of cardiac output and systemic vascular resistance:
MAP = CO × SVR
This explains many clinical situations. If cardiac output falls, for example after a heart attack, the body compensates by increasing vascular resistance to protect MAP. If resistance drops, as in septic shock, MAP falls even when cardiac output is normal or high. Regulation is handled by baroreceptors in the carotid sinus and aortic arch, which use negative feedback to keep MAP in its ideal range.
Related reading: to understand the CO part of this equation, see our guide on the cardiac output formula (CO = HR × SV).
Why Is a MAP of 65 mmHg Important in Sepsis?
The Surviving Sepsis Campaign 2021 guideline recommends, for adults with septic shock on vasopressors, an initial MAP target of 65 mmHg rather than a higher target. It also recommends norepinephrine as the first-line vasopressor.
The reasoning comes from clinical trials. In the SEPSISPAM trial, 776 patients were randomised, and a higher MAP target of 80 to 85 mmHg did not improve survival compared with 65 to 70 mmHg. MAP values below 60 mmHg are linked with decreased organ perfusion.
One nuance matters in practice. In SEPSISPAM, patients with long-standing hypertension had better kidney outcomes with the higher target, so clinicians sometimes individualise the goal for these patients.
MAP and Cerebral Perfusion Pressure (CPP)
In head injury and neurocritical care, MAP is used to calculate the pressure that drives blood to the brain:
CPP = MAP − ICP (intracranial pressure)
Normal CPP lies between 60 and 80 mmHg, and because ICP is a small number in healthy people, CPP depends mostly on MAP. A fall in MAP can therefore reduce brain perfusion quickly when ICP is raised.
Healthy brains also use autoregulation. Cerebral blood flow stays fairly constant across a MAP of about 60 to 150 mmHg, but this protection can fail in injury or critical illness.
MAP vs Blood Pressure: What Is the Difference?
| Feature | Blood Pressure (BP) | Mean Arterial Pressure (MAP) |
|---|---|---|
| What it shows | Peak and lowest pressure (SBP/DBP) | Average pressure over one cycle |
| Written as | Two numbers, e.g. 120/80 | One number, e.g. 93 mmHg |
| Best used for | Screening and routine monitoring | Perfusion in ICU, sepsis, shock |
Limitations of the MAP Formula
- Heart rate and rhythm: the standard formula assumes a normal heart rate and regular rhythm. With fast heart rates or arrhythmias, the true MAP from an arterial line can differ from the calculated value.
- Invasive monitoring: in critically ill patients, MAP is usually read directly from an arterial line or monitor and not calculated by hand.
- Individual baseline: a “normal” MAP for a young healthy adult may be inadequate for someone with chronic hypertension.
- Not a stand-alone test: MAP should be read with lactate, urine output, mental status and skin perfusion.
Key Takeaways
- MAP = DBP + ⅓ (SBP − DBP), or (SBP + 2 × DBP) ÷ 3.
- Normal MAP is about 70 to 100 mmHg.
- MAP = CO × SVR, so both pump function and vessel tone determine it.
- In septic shock, an initial MAP target of 65 mmHg is recommended.
- CPP = MAP − ICP, which links MAP to brain perfusion.
Frequently Asked Questions
What is the MAP formula? MAP = DBP + ⅓ (SBP − DBP).
What is a normal MAP? Roughly 70 to 100 mmHg in adults.
Is a MAP of 65 mmHg good or bad? It is the minimum target used in septic shock. In a healthy person, 65 is on the low side of normal, and the clinical context matters.
What is the MAP for 120/80? 93.3 mmHg.
How is MAP different from average blood pressure? MAP is a weighted average that gives more weight to diastolic pressure because the heart spends more time in diastole.
Can I calculate MAP at home? Yes, from any blood pressure reading, but home values are for education only. Medical decisions must be made with a doctor.
Mean Arterial Pressure (MAP) Knowledge Quiz
Available options: 1 to 20
Disclaimer: This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment.
