Systolic (mmHg)

Diastolic (mmHg)

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MAP readings compared against the 65 mmHg perfusion threshold — 130/70 gives a MAP of 90.0 mmHg, lower than 120/80 despite the higher systolic.

Method & verification

How This Tool Works

fact-checked against our calculation methodology

Calculation Method

MAP = (Systolic + 2 × Diastolic) ÷ 3

Site methodology

BoringToolsKit methodology and verification standard

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Assumptions to Verify

These tools provide general estimates for planning and education only.
They are not medical advice and not a substitute for a qualified healthcare professional.
Always consult your doctor or another healthcare provider about your specific situation.

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Worked example: where the extra weight on diastolic comes from

Take a reading of 120/80 mmHg. The formula gives MAP = (SBP + 2 x DBP) / 3 = (120 + 2 x 80) / 3 = (120 + 160) / 3 = 280 / 3 = 93.3 mmHg. The doubling is not cosmetic: the heart spends roughly two thirds of each cycle in diastole, so the diastolic pressure gets two of the three parts in the weighted average.

A second reading shows how sensitive the result is to diastolic changes. At 130/70 the MAP is (130 + 140) / 3 = 270 / 3 = 90.0 mmHg, lower than at 120/80 despite the higher systolic value. That is why the tool rejects diastolic values at or above systolic: a diastolic of 120 with a systolic of 110 would produce a MAP of about 116.7 mmHg from a physiologically impossible input, which would look like a healthy result and hide the data entry error.

What the formula leaves out

The (SBP + 2 x DBP) / 3 approximation assumes the arterial pressure waveform is triangular, which holds reasonably well at normal heart rates. At tachycardia the systolic portion occupies a larger fraction of the cycle, and the true MAP drifts closer to (SBP + DBP) / 2, so a patient at 140/85 with a heart rate of 130 may have a real MAP nearer 103 than the 103.3 versus 110 gap suggests. Studies comparing the formula against invasive arterial lines report typical errors of about 5 mmHg, larger in sepsis and arrhythmia.

The 65 mmHg threshold is also a population average, not a personal one. Chronically hypertensive patients autoregulate upward, and some maintain organ perfusion at MAP values of 75 to 80 mmHg while dropping below their usual baseline; others, including many patients on chronic beta blockade, tolerate 60 to 62 mmHg. An arterial line, which measures MAP directly beat by beat, is the reference standard in ICU settings precisely because cuff-derived estimates carry this margin of error.