Why use MAP instead of systolic BP?

MAP is the true driving pressure for organ perfusion. SBP can be misleadingly 'normal' when pulse pressure is wide (e.g. SBP 100, DBP 40 → MAP 60 — perfusion inadequate despite SBP appearing borderline acceptable).

What MAP should I target post-ROSC?

ARC and AHA guidelines recommend a MAP of ≥65 mmHg post-ROSC. Some centres target MAP ≥70–80 mmHg depending on suspected aetiology. Avoid hypotension and excessive hypertension — both worsen neurological outcomes.

Does MAP change with heart rate?

The ⅓/⅔ formula assumes a normal heart rate where diastole is approximately twice as long as systole. At very high heart rates (>150 bpm), diastole shortens relatively — MAP may be slightly underestimated by the standard formula.

Mean Arterial Pressure (MAP) — Free Paramedics Calculator

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Post-cardiac arrest ROSC, 68-year-old. BP 88/52. The receiving team asks for MAP on handover — you need the number in 10 seconds.

Mean Arterial Pressure (MAP)

Haemodynamics

Systolic BP (mmHg)

Diastolic BP (mmHg)

MAP = DBP + ⅓ × (SBP − DBP) Normal MAP: 70–100 mmHg
MAP <60 mmHg = inadequate cerebral and renal perfusion
MAP ≥65 mmHg is the target in septic shock (Surviving Sepsis Campaign)

Reference: NCBI — Mean Arterial Pressure · Surviving Sepsis Campaign Guidelines

⚕️ Clinical safety: 🇦🇺 Verify with facility drug formulary and senior clinician · Meets AHPRA/ACSQHC standards

1 What this calculator does

Calculates Mean Arterial Pressure (MAP) from systolic and diastolic blood pressure. MAP is the true average perfusion pressure driving blood to organs — more clinically meaningful than SBP or DBP alone. Flags hypoperfusion below 65 mmHg.

2 Formula & professional reasoning

MAP = DBP + ⅓(SBP − DBP) = DBP + ⅓(Pulse Pressure) | Also: MAP = (SBP + 2×DBP) ÷ 3

MAP is weighted toward diastolic pressure because the heart spends approximately two-thirds of the cardiac cycle in diastole. At normal heart rates, the ⅓ weighting reflects this ratio. MAP represents the constant component of arterial pressure that drives flow through the peripheral vasculature. A MAP of 65 mmHg is the widely-used threshold for adequate organ perfusion in sepsis, post-ROSC and haemodynamic shock management.

3 Worked examples

⚠️ Illustrative example only — not clinical or professional instruction.

Basic

Normal blood pressure

Given: SBP 120, DBP 80

Working: 80 + (120-80)/3 = 80 + 13.3

Answer: MAP 93 mmHg — Normal perfusion

💡 Normal MAP 70–100 mmHg. No intervention required.

Standard

Post-ROSC hypotension

Given: SBP 88, DBP 52

Working: 52 + (88-52)/3 = 52 + 12

Answer: MAP 64 mmHg — Borderline — below 65 threshold

💡 MAP just below 65 mmHg threshold. Consider vasopressor support. Pre-alert destination.

Advanced

Hypertensive emergency

Given: SBP 210, DBP 130

Working: 130 + (210-130)/3 = 130 + 26.7

Answer: MAP 157 mmHg — Severely elevated

💡 MAP >150 mmHg in context of symptoms = hypertensive emergency. Gradual controlled reduction — avoid dropping >25% in first hour.

4 Sanity check

MAP ≥ 65 mmHg

Adequate organ perfusion threshold

Used in sepsis (surviving sepsis campaign), post-ROSC and haemodynamic resuscitation targets.

MAP < 65 mmHg

Organ hypoperfusion risk

Brain, kidneys, heart at risk. Consider vasopressors, IV fluid, cause-directed treatment.

MAP 70–100 mmHg

Normal adult range

MAP > 150 mmHg

Hypertensive crisis threshold

In context of end-organ symptoms (chest pain, altered consciousness, visual changes) = emergency.

5 Common errors

Error	Cause	Consequence	Fix
Using SBP as surrogate for perfusion	Habit — SBP is the most commonly quoted value	MAP overestimates or underestimates perfusion depending on pulse pressure	Always calculate MAP when assessing haemodynamic adequacy — especially post-ROSC and in sepsis
Targeting SBP >90 instead of MAP ≥65	Older clinical guidelines	Permissive hypotension when SBP 90–95 but MAP <65 (wide pulse pressure)	Post-ROSC target is MAP ≥65 mmHg per international resuscitation guidelines
Using non-invasive BP in arrhythmia	Automated cuff reads incorrectly in AF or irregular rhythms	MAP calculation based on erroneous BP	Take multiple readings, use manual auscultation, and correlate with clinical signs
Not trending MAP	Single measurement only	Haemodynamic trajectory missed	Calculate MAP at first contact, post-intervention and at handover to track response to treatment