Cerebral Perfusion Pressure Calculator (CPP = MAP − ICP)

Understanding the cerebral perfusion pressure calculator — concept and principle

This calculator works out cerebral perfusion pressure (CPP), the pressure driving blood through the brain, from mean arterial pressure and intracranial pressure. It estimates MAP from systolic and diastolic pressure if no measured value is given, and compares CPP with the 60–70 mmHg target and ICP with the 22 mmHg treatment threshold used in severe traumatic brain injury. Neurocritical-care staff and students use it.

Pressure pushing blood into the brain — with the default inputs: CPP 70.3 mmHg.

How it is calculated

MAP (if not measured) = diastolic + (systolic − diastolic) ÷ 3
CPP = MAP − ICP
Target CPP 60–70 mmHg; ICP above 22 mmHg is the treatment threshold (Brain Trauma Foundation, 4th edition)

The principle

Blood flows into the brain because arterial pressure is higher than the pressure inside the skull. When the brain swells, intracranial pressure rises and the pressure difference, CPP, falls; too low a CPP risks inadequate blood flow. The Brain Trauma Foundation guidelines recommend a CPP target of 60–70 mmHg in severe traumatic brain injury, considering the patient's autoregulation, and advise against aggressive fluids or vasopressors to keep CPP above 70 because of the risk of lung injury.

Worked example

Defaults: systolic 125, diastolic 70, no measured MAP, ICP 18.

MAP = 70 + (125 − 70) ÷ 3 = 88.33…, shown as 88.3 mmHg.
CPP = 88.33 − 18 = 70.33…, shown as 70.3 mmHg.
Because 70.3 is just above 70: Above the target.
ICP 18 is not above 22: No.

Each point is the calculator re-run with only “Intracranial pressure, ICP (mmHg)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Intracranial pressure, ICP (mmHg)	Cerebral perfusion pressure (mmHg)
4.5	83.8
9	79.3
13.5	74.8
18	70.3
22.5	65.8
27	61.3
36	52.3

How to read the result

Where does your result fall?

Here CPP lies at the upper edge of the target, which in practice is close to target; the label is "above" because 70.3 is just over 70. ICP is below the treatment threshold. Intensive-care teams adjust targets to each patient, monitor trends continuously and use other measures such as brain oxygen where available.

Common mistakes

Estimating MAP from cuff readings when an arterial line is in place.
Using ICP values from a different time from the blood pressure.
Applying adult targets to children.
Treating CPP targets as fixed for all brain conditions.

Keep in mind: Not medical advice. ICP can only be measured with a monitor in or on the brain; this calculation belongs to intensive-care settings.

Frequently asked questions

What is a normal cerebral perfusion pressure?

In severe traumatic brain injury, guidelines target 60–70 mmHg.

How is MAP estimated?

Diastolic plus one third of the difference between systolic and diastolic.

What ICP needs treatment?

The Brain Trauma Foundation recommends treating ICP above 22 mmHg.

Sources: Brain Trauma Foundation, Guidelines for the Management of Severe Traumatic Brain Injury, 4th edition (Carney N et al., Neurosurgery 2017;80:6–15)

Checked 9 Nov 2026. Brain Trauma Foundation, Guidelines for the Management of Severe Traumatic Brain Injury, 4th edition (Carney N et al., Neurosurgery 2017;80:6–15): CPP target 60–70 mmHg (level IIB), avoid aggressive measures to keep CPP above 70 mmHg (level III), treat ICP above 22 mmHg (level IIB) — as summarised in Allegheny Health Network, “TBI Guidelines”, Pulmonary & Critical Care Conference 2024; MAP formula from Edwards “Normal Haemodynamic Parameters” (2022).

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