What is cerebral perfusion pressure?

Cerebral perfusion pressure (CPP) is the pressure gradient that drives blood flow through the brain. It is calculated as CPP = MAP - ICP, where MAP is mean arterial pressure and ICP is intracranial pressure. A normal CPP in adults is approximately 60 to 100 mmHg. CPP below 50 mmHg is associated with ischaemia and poor outcomes in brain-injured patients. Clinical guidelines for traumatic brain injury (TBI) typically target a CPP of at least 60 mmHg, with some protocols aiming for 60 to 70 mmHg.

How is mean arterial pressure (MAP) calculated?

Mean arterial pressure is calculated as MAP = DBP + (SBP - DBP) / 3, where SBP is systolic blood pressure and DBP is diastolic blood pressure. This formula reflects the fact that the heart spends approximately one-third of the cardiac cycle in systole and two-thirds in diastole. For example, with SBP 120 mmHg and DBP 80 mmHg: MAP = 80 + (120 - 80) / 3 = 80 + 13.3 = 93.3 mmHg. An equivalent formula is MAP = (SBP + 2 x DBP) / 3, which gives the same result.

What happens when CPP is too low or too high?

When CPP falls below approximately 50 to 60 mmHg, the brain's autoregulatory mechanisms may be overwhelmed, resulting in reduced cerebral blood flow and ischaemia. In traumatic brain injury management, a CPP below 60 mmHg is a recognised threshold for intervention. Conversely, CPP above 70 mmHg may increase cerebral blood volume and exacerbate raised intracranial pressure in some patients, particularly if cerebral autoregulation is impaired. The optimal CPP target depends on the individual clinical context and should be determined by a specialist.

Cerebral Perfusion Pressure Calculator

Calculate cerebral perfusion pressure (CPP) from mean arterial pressure (MAP) and intracranial pressure (ICP). Enter your blood pressure readings and ICP value to get CPP instantly using the standard formula CPP = MAP - ICP.

MAP is calculated automatically from your systolic and diastolic blood pressure values using the formula MAP = DBP + (SBP - DBP) / 3.

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Method verified June 2026 Standard clinical formula. CPP = MAP - ICP. Brain Trauma Foundation guidelines.

1. Blood Pressure

Systolic blood pressure (SBP) mmHg

mmHg

Diastolic blood pressure (DBP) mmHg

mmHg

MAP entry method

Mean arterial pressure (MAP) mmHg

mmHg

2. Intracranial Pressure

Intracranial pressure (ICP) mmHg

mmHg

ICP source for reference only

CPP = MAP - ICP

MAP = DBP + (SBP - DBP) / 3

Cerebral Perfusion Pressure Result

MAP

Mean arterial pressure

ICP

Intracranial pressure

CPP
-
Cerebral perfusion pressure

CPP Status

Relative to 60 mmHg threshold

Enter values above to see interpretation.

Calculation Breakdown

Systolic BP (SBP)-

Diastolic BP (DBP)-

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

Intracranial pressure (ICP)-

CPP = MAP - ICP-

Clinical Reference Ranges

CPP Range	Interpretation
< 50 mmHg	Critical: severe ischaemia risk
50 to 59 mmHg	Low: below TBI treatment threshold
60 to 70 mmHg	Target range for TBI management
70 to 100 mmHg	Normal adult range
> 100 mmHg	High: possible hyperaemia

Normal ICP is 5 to 15 mmHg. Raised ICP is generally defined as > 20 mmHg.

How Cerebral Perfusion Pressure Is Calculated

Cerebral perfusion pressure (CPP) is the net pressure gradient that drives cerebral blood flow through the brain. It is defined as the difference between mean arterial pressure (MAP) and intracranial pressure (ICP):

CPP = MAP - ICP

MAP is calculated from systolic blood pressure (SBP) and diastolic blood pressure (DBP) using:

MAP = DBP + (SBP - DBP) / 3

This formula accounts for the fact that diastole occupies roughly two-thirds of the cardiac cycle. An equivalent form is MAP = (SBP + 2 x DBP) / 3, which gives the same result.

Worked Example

With SBP = 120 mmHg, DBP = 80 mmHg, and ICP = 10 mmHg:

MAP = 80 + (120 - 80) / 3 = 80 + 13.3 = 93.3 mmHg
CPP = 93.3 - 10 = 83.3 mmHg
This CPP of 83.3 mmHg is within the normal adult range (60 to 100 mmHg).

Clinical Significance of CPP

CPP is a critical parameter in the management of traumatic brain injury (TBI), stroke, and other conditions associated with raised intracranial pressure. The Brain Trauma Foundation's guidelines for severe TBI recommend maintaining CPP between 60 and 70 mmHg. Below 60 mmHg, cerebral blood flow may become inadequate to meet the brain's metabolic demands, risking ischaemia. Above 70 mmHg, there is a risk of exacerbating cerebral oedema if autoregulation is impaired.

Normal ICP and Raised ICP

Normal intracranial pressure in adults lies between 5 and 15 mmHg when supine. ICP above 20 mmHg is considered raised and typically warrants treatment. Common causes of raised ICP include traumatic brain injury, intracranial haemorrhage, hydrocephalus, brain tumours, and severe meningitis. Raised ICP directly reduces CPP, so managing ICP is central to preserving cerebral perfusion.

Autoregulation

Under normal conditions, the brain autoregulates cerebral blood flow to keep it relatively constant over a CPP range of approximately 50 to 150 mmHg. Outside this range, or when autoregulation is impaired by injury, cerebral blood flow becomes pressure-passive and directly proportional to CPP. In these situations, even small reductions in MAP or increases in ICP can cause significant reductions in cerebral blood flow.

Important Note

This calculator is for educational and reference purposes only. Accurate ICP measurement requires invasive monitoring (intraventricular catheter or intraparenchymal probe) performed in a clinical setting. Clinical decisions regarding CPP targets should be made by qualified medical professionals based on the full clinical picture, including neurological examination, imaging, and continuous monitoring. Do not use this calculator as a substitute for clinical assessment or treatment guidance.

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Sources and method: Brain Trauma Foundation. Guidelines for the Management of Severe Traumatic Brain Injury, 4th edition (2016). Rangel-Castilla L et al. Cerebral pressure autoregulation in traumatic brain injury. Neurosurg Focus, 2008. Steiner LA, Andrews PJ. Monitoring the injured brain: ICP and CBF. British Journal of Anaesthesia, 2006. Formula: CPP = MAP - ICP; MAP = DBP + (SBP - DBP) / 3 (standard clinical definitions).

This calculator is for educational reference only and does not constitute medical advice. Cerebral perfusion pressure monitoring and treatment decisions require clinical assessment by qualified medical professionals. ICP values used in this calculator should be obtained from validated invasive monitoring equipment in appropriate clinical settings.