Nursing care
MAP calculation in nursing: the formula, the normal range and why 65 is the line
Written and reviewed by Kevin Patel, MSN, RN, CCRN · 4 min read · Updated November 2026
Short answer
Mean arterial pressure (MAP) is calculated as diastolic pressure plus one third of the pulse pressure (systolic minus diastolic). A normal MAP sits roughly between 70 and 110 mm Hg. In shock, a MAP under 65 mm Hg counts as hypotension, and in septic shock vasopressors are titrated to keep it at 65 or above.
The formula, written two ways that give the same answer
OpenStax Anatomy and Physiology gives MAP as diastolic pressure plus one third of the difference between systolic and diastolic. That difference is the pulse pressure. Its example of 120/80 gives 80 plus 40 divided by 3, about 93 mm Hg.
| Item | Value or formula | Source context |
|---|---|---|
| MAP formula | DBP + (SBP minus DBP) divided by 3 | OpenStax physiology text |
| Same formula rearranged | (SBP + 2 x DBP) divided by 3 | Algebra of the line above |
| Normal range | About 70 to 110 mm Hg | OpenStax |
| Hypotension in shock | MAP under 65 mm Hg (or SBP under 90) | MSD Manual, Shock |
| Septic shock target | MAP at or above 65 mm Hg with vasopressors | MSD Manual, Sepsis |
The second version is just the first rearranged, so use whichever you can do faster without a calculator. Both count diastolic pressure twice and systolic once, which is why MAP is not the simple average of the two numbers. Averaging them is the most common wrong answer on calculation items.
Worked examples: when a passable systolic hides a low MAP
These are hypothetical practice readings, not patient data. Round MAP to the nearest whole number at the end, and keep units in mm Hg throughout.
Worked example
- Pulse pressure: 90 minus 50 = 40 mm Hg
- One third of 40 = 13.3 mm Hg
- 50 + 13.3 = 63.3 mm Hg
Worked example
- Pulse pressure: 104 minus 44 = 60 mm Hg
- One third of 60 = 20 mm Hg
- 44 + 20 = 64 mm Hg
- Check with the rearranged formula: (104 + 88) divided by 3 = 64 mm Hg
Reading 2 is the point of the page. A systolic of 104 looks acceptable at a glance, but the low diastolic drags MAP under 65. Averaging the two numbers, 104 plus 44 divided by 2, gives 74 and would wrongly suggest the patient is above target. In a septic patient on a vasopressor, that error could delay a titration.
Why 65 is the number in shock, and when the target is lower
OpenStax explains that if MAP stays below about 60 mm Hg for an extended time, pressure is not high enough to push blood through the tissues, and ischemia follows. MSD Manual's shock chapter uses a MAP under 65 or a systolic under 90 as its working definition of hypotension, while noting shock can exist before the pressure falls.
For septic shock, MSD Manual defines the condition as needing vasopressors to hold MAP at 65 or above with a lactate over 2 mmol/L despite fluids, and describes titrating norepinephrine to at least 65. Hemorrhagic shock is different: until the bleeding is controlled, MSD describes a deliberately lower goal of MAP 55 to 60. So 65 is a sepsis and general shock target, not a rule for every patient; the prescriber sets the goal.
What a falling MAP looks like at the bedside
MAP is one number among several perfusion signs. MSD lists oliguria, under about 0.5 mL/kg/hr, and a lactate above 2 mmol/L as markers of poor tissue perfusion. A nurse recording a MAP of 63 should look for these, along with confusion, cool skin and a rising heart rate, before calling.
Report a MAP below the ordered target, a downward trend over several readings, or a MAP that falls after a vasopressor rate change. Recheck a single surprising value by cuff position and size before escalating, but do not wait for a second reading if the patient also looks worse.
Sources and further reading
20.2 Blood Flow, Blood Pressure, and Resistance (OpenStax Anatomy and Physiology 2e). MAP formula and 120/80 example; normal MAP 70 to 110 mm Hg; below 60 mm Hg for an extended time leads to ischemia; pulse pressure definition.
Shock (MSD Manual Professional Edition). Hypotension as SBP under 90 or MAP under 65 and not required for shock; hemorrhagic shock goal MAP 55 to 60; oliguria under 0.5 mL/kg/hr and lactate over 2 mmol/L as hypoperfusion markers.
Sepsis and Septic Shock (MSD Manual Professional Edition). Septic shock definition with vasopressors to maintain MAP at 65 or above and lactate over 2 mmol/L; vasopressors given to raise mean pressure to at least 65.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our cardiovascular practice questions are the closest set to what this page covers.
Common questions
How do you calculate MAP?
Subtract diastolic from systolic to get pulse pressure, divide that by 3, then add it to the diastolic. For 120/80, that is 80 plus 13.3, about 93 mm Hg. The same answer comes from adding systolic to twice the diastolic and dividing by 3.
What MAP is too low?
In shock and sepsis care, a MAP under 65 mm Hg is treated as hypotension, and OpenStax notes that sustained values below about 60 risk tissue ischemia. Targets can differ by condition, such as the lower goal used in uncontrolled bleeding, so follow the ordered range.
Why is MAP 65 the target?
It is the threshold commonly used to define hypotension in shock and the level vasopressors are titrated to in septic shock. Below roughly 60 mm Hg, pressure may be too low to keep blood flowing through organs, which is why vasopressors are titrated to hold at least 65 rather than 60.
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