MAP Calculator
Free Mapcalculator Calculator with medically-sourced formulas. Enter your measurements for personalized, accurate health insights.
Formula
MAP = DBP + (SBP - DBP) / 3
Where MAP = Mean Arterial Pressure, SBP = Systolic Blood Pressure, DBP = Diastolic Blood Pressure. This formula reflects that approximately one-third of the cardiac cycle is spent in systole and two-thirds in diastole at normal heart rates. Can also be expressed as MAP = (SBP + 2 x DBP) / 3.
Worked Examples
Example 1: Normal Blood Pressure MAP Calculation
Problem: A healthy 35-year-old has BP 120/80 mmHg with HR 72 bpm. Calculate MAP, pulse pressure, and shock index.
Solution: MAP = DBP + (SBP - DBP) / 3\nMAP = 80 + (120 - 80) / 3\nMAP = 80 + 13.3 = 93.3 mmHg\n\nPulse Pressure = SBP - DBP = 120 - 80 = 40 mmHg\nShock Index = HR / SBP = 72 / 120 = 0.60
Result: MAP: 93.3 mmHg (Normal) | Pulse Pressure: 40 mmHg | Shock Index: 0.60 (Normal)
Example 2: Hypotensive Patient in Septic Shock
Problem: A 68-year-old septic patient has BP 85/50 mmHg with HR 118 bpm. Calculate MAP and assess hemodynamic status.
Solution: MAP = DBP + (SBP - DBP) / 3\nMAP = 50 + (85 - 50) / 3\nMAP = 50 + 11.7 = 61.7 mmHg\n\nPulse Pressure = 85 - 50 = 35 mmHg\nShock Index = 118 / 85 = 1.39\nCPP estimate (ICP ~10) = 61.7 - 10 = 51.7 mmHg
Result: MAP: 61.7 mmHg (Low) | Shock Index: 1.39 (Elevated - Shock) | Vasopressor support needed
Frequently Asked Questions
How is MAP calculated and what does the formula represent?
MAP is calculated using the formula MAP = DBP + (SBP - DBP) / 3, which can also be written as MAP = (SBP + 2 x DBP) / 3. This formula reflects the physiological fact that during a normal cardiac cycle at resting heart rates, approximately one-third of the time is spent in systole and two-thirds in diastole. Therefore, diastolic pressure contributes twice as much to the mean pressure as systolic pressure. This approximation is most accurate at normal heart rates around 60-80 beats per minute. At significantly elevated heart rates, the systolic phase occupies a proportionally larger portion of the cardiac cycle, and the formula becomes less accurate. Direct MAP measurement using an arterial catheter provides continuous real-time data and is preferred in critically ill patients.
How does MAP relate to cerebral perfusion pressure?
Cerebral perfusion pressure (CPP) is calculated as MAP minus intracranial pressure (ICP), making MAP a critical determinant of brain blood flow. Normal ICP ranges from 5-15 mmHg, so a MAP of 80 mmHg with normal ICP yields a CPP of approximately 65-75 mmHg, which is adequate for cerebral perfusion. In patients with traumatic brain injury or other causes of elevated ICP, maintaining adequate MAP becomes essential to prevent secondary brain injury from ischemia. Current guidelines recommend maintaining CPP between 60-70 mmHg in TBI patients. If ICP rises to 25 mmHg, the MAP must be at least 85-95 mmHg to maintain adequate CPP. This relationship explains why hypotension is particularly dangerous in patients with intracranial pathology.
What is the relationship between MAP and systemic vascular resistance?
MAP, cardiac output, and systemic vascular resistance (SVR) are related by the equation MAP = CO x SVR + CVP, where CO is cardiac output and CVP is central venous pressure. This relationship is analogous to Ohm law in electrical circuits where voltage equals current times resistance. SVR represents the total resistance to blood flow in the systemic circulation, primarily determined by arteriolar tone. In clinical practice, if MAP drops due to vasodilation (low SVR) as in septic shock, vasopressors are used to increase SVR. If MAP drops due to pump failure (low CO) as in cardiogenic shock, inotropes are used to increase contractility. Understanding which component is abnormal is essential for choosing appropriate hemodynamic support and avoiding treatments that could worsen the underlying problem.
How do vasopressors target MAP in critical care settings?
Vasopressors are medications used in critical care to raise MAP to target levels, typically 65 mmHg or above in septic shock. Norepinephrine is the first-line vasopressor, acting primarily on alpha-1 receptors to increase SVR with some beta-1 activity to support cardiac output. Vasopressin acts on V1 receptors to cause vasoconstriction through a catecholamine-independent pathway and is often added as a second agent. Phenylephrine is a pure alpha-1 agonist used when tachycardia limits norepinephrine use. Epinephrine provides both alpha and beta stimulation and is used for refractory shock or combined cardiogenic-distributive shock. The choice of vasopressor depends on the underlying cause of hypotension, cardiac rhythm, and individual patient factors. MAP is monitored continuously via arterial catheter, and vasopressor doses are titrated to maintain target perfusion pressure.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
What formula does MAP Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.