Cerebral Perfusion Pressure Calculator
This calculator works out cerebral perfusion pressure (CPP), the pressure gradient driving blood flow through the brain, using the standard clinical formula CPP = MAP - ICP. Enter your systolic and diastolic blood pressure (SBP and DBP) and the tool automatically derives mean arterial pressure (MAP) using MAP = DBP + (SBP - DBP) / 3, or switch to manual entry if you already have a measured MAP reading. Then enter intracranial pressure (ICP), normally obtained from an invasive ICP monitor in a clinical setting. The calculator returns MAP, ICP and the resulting CPP in mmHg, plus a status reading that flags where your result sits against clinical thresholds: critical (below 50 mmHg), low (50 to 59 mmHg), the 60 to 70 mmHg target range used in traumatic brain injury management, the normal adult range (60 to 100 mmHg), and high (above 100 mmHg), alongside a full calculation breakdown and a clinical reference table. Use it to quickly check CPP from bedside readings, or to see how changes in blood pressure or ICP affect cerebral perfusion. This calculator is for educational and reference purposes only. It does not replace continuous clinical monitoring, and CPP targets and treatment decisions should always be made by qualified medical professionals based on the full clinical picture.
1. Blood Pressure
2. Intracranial Pressure
Calculation Breakdown
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):
MAP is calculated from systolic blood pressure (SBP) and diastolic blood pressure (DBP) using:
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.