Blood Pressure Calculator
Enter your top (systolic) and bottom (diastolic) numbers to see your blood-pressure category, plus your mean arterial pressure (MAP) and pulse pressure. Switch between the US (ACC/AHA 2017) and European (ESC/ESH 2018) guidelines, and average a second reading for a more reliable result.
Formula
Worked example
A reading of 135/75 mmHg under ACC/AHA 2017: systolic (135) sits in the 130-139 Stage 1 band while diastolic (75) is below 80, so the category follows the higher number and the result is Stage 1 Hypertension. MAP = (135 + 2 x 75) / 3 = 95 mmHg, and pulse pressure = 135 - 75 = 60 mmHg.
How blood pressure is classified
Blood pressure is written as two numbers: systolic (the pressure while your heart beats) over diastolic (the pressure while it rests between beats), both measured in millimetres of mercury (mmHg). This calculator supports the two leading guidelines. The 2017 American College of Cardiology and American Heart Association (ACC/AHA) guideline sorts readings into Normal, Elevated, Stage 1, Stage 2 and Hypertensive Crisis. The 2018 European Society of Cardiology and Society of Hypertension (ESC/ESH) guideline uses Optimal, Normal, High-normal and Grade 1 to 3. Under both systems a reading is placed in the more severe category whenever either number reaches that threshold, so 124/92 mmHg counts as high because the diastolic value alone qualifies, even though the systolic looks only mildly elevated.
Mean arterial pressure and pulse pressure
Beyond the category, the calculator reports two derived measures clinicians use. Mean arterial pressure (MAP) is the average pressure over a full heartbeat, estimated as (systolic + 2 x diastolic) / 3. Diastole lasts about twice as long as systole, which is why the formula weights the diastolic value double. A MAP of roughly 70 to 100 mmHg is considered adequate to perfuse the organs in a resting adult. Pulse pressure is simply systolic minus diastolic; a value near 40 mmHg is typical, while a persistently wide pulse pressure (over about 60 mmHg) can reflect stiffer arteries and is itself a cardiovascular risk marker.
Why averaging matters and why one reading is not a diagnosis
Blood pressure naturally swings throughout the day and rises with stress, caffeine, exercise, a full bladder, or even the anxiety of being measured. Guidelines therefore recommend taking two or more readings a minute or two apart and using their average, which this calculator does when you turn on the second reading. Even so, hypertension is diagnosed from readings on several different days, ideally after sitting quietly for five minutes with your back supported and feet flat. Use this tool to understand where a measurement falls, not as a standalone medical verdict.
What the categories mean for you
Normal and Optimal readings call for maintaining healthy habits. Elevated, High-normal and Stage 1 or Grade 1 hypertension are usually addressed first with lifestyle changes, reducing sodium, moving more, limiting alcohol, managing weight and stress, with medication considered when overall cardiovascular risk is high. Stage 2 and Grade 2 to 3 typically warrant medication alongside those changes. A reading above 180/120 mmHg (Crisis or Grade 3) needs prompt attention, and urgent care if you have symptoms such as chest pain, breathlessness, or neurological changes. Readings below 90/60 mmHg are flagged as low and matter mainly when they cause dizziness or fainting.
Blood pressure categories by guideline
| ACC/AHA 2017 (US) | Systolic | Diastolic | ESC/ESH 2018 (EU) |
|---|---|---|---|
| Normal | Below 120 | and below 80 | Optimal / Normal |
| Elevated | 120-129 | and below 80 | Normal |
| Stage 1 | 130-139 | or 80-89 | High-normal / Grade 1 |
| Stage 2 | 140-179 | or 90-109 | Grade 1 / Grade 2 |
| Crisis | 180 or higher | or 120 or higher | Grade 3 (180+/110+) |
A reading is classified by whichever number reaches the higher band. The US (ACC/AHA 2017) and European (ESC/ESH 2018) systems use different cutoffs, so the same reading can fall in different categories.
Frequently asked questions
What is the difference between the ACC/AHA and ESC/ESH guidelines?
The US ACC/AHA 2017 guideline labels 130/80 mmHg and above as Stage 1 hypertension. The European ESC/ESH 2018 guideline keeps the older 140/90 threshold for diagnosing hypertension (Grade 1) and adds an Optimal and a High-normal band below it. The same reading can therefore land in different categories depending on the guideline, which is why this calculator lets you switch between them.
What are MAP and pulse pressure, and why do they matter?
Mean arterial pressure (MAP) is the average pressure in your arteries over one heartbeat, calculated as (systolic + 2 x diastolic) / 3; about 70 to 100 mmHg is normal at rest and a MAP of at least 60 to 65 mmHg is generally needed to perfuse the organs. Pulse pressure is systolic minus diastolic, typically around 40 mmHg. A wide pulse pressure can indicate stiffer arteries and added cardiovascular risk.
Should I average my blood pressure readings?
Yes. A single reading is easily skewed by stress, caffeine, or movement, so guidelines recommend taking two or more measurements a minute or two apart and using the average. Turn on the second-reading option here to average two readings. For a diagnosis, clinicians average readings taken on several different days.
Which number matters more, systolic or diastolic?
Both matter, and your category is set by whichever number reaches the higher band. In adults over 50, systolic pressure tends to be the stronger predictor of heart risk because arteries stiffen with age, while elevated diastolic pressure is especially relevant in younger people.
Can this calculator diagnose high blood pressure?
No. It classifies your reading using published thresholds and shows derived measures, but a diagnosis requires multiple accurate measurements over time, interpreted by a clinician who also weighs your overall health. Use the result as information to discuss with your doctor, not as a diagnosis or treatment decision.