Blood Pressure Calculator
Classify a blood-pressure reading by the ACC/AHA categories, with MAP, pulse pressure and guidance.
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—Where your reading falls
Blood pressure categories (ACC/AHA)
What this means & what to do
How to use the Blood Pressure Calculator
Step 1 — Enter your reading
- Type your systolic (top) and diastolic (bottom) numbers in mmHg.
- Use an average of two or three good readings if you have them.
Step 2 — Read your category
- See your ACC/AHA category, with the higher of the two numbers deciding it.
- Check the colour-coded gauge and the systolic/diastolic position bars.
Step 3 — Understand the detail
- Review MAP, pulse pressure and the full category reference table.
- Read the tailored guidance for your result.
Step 4 — Act & share
- Download a PDF to discuss with your doctor.
- Re-measure properly before drawing conclusions.
Frequently asked questions
The top number (systolic) is the pressure in your arteries while the heart beats and pushes blood out. The bottom number (diastolic) is the pressure between beats, while the heart rests and refills. Both matter, and a reading is written as systolic "over" diastolic, for example 120/80 mmHg.
It uses the 2017 American College of Cardiology / American Heart Association (ACC/AHA) categories: Normal, Elevated, Stage 1 hypertension, Stage 2 hypertension and Hypertensive crisis. Note that some countries (for example those following ESC/ESH or NICE guidance) define hypertension at slightly higher thresholds, so a reading labelled "Stage 1" here might be called "high-normal" elsewhere.
The higher of the two categories applies. For example, 118/92 has a normal systolic but a Stage 2 diastolic, so the overall reading is Stage 2. The tool always reports the more serious of the two.
No. Blood pressure naturally varies through the day and rises with stress, pain, caffeine, exercise, a full bladder, talking, or a cold room. A diagnosis of hypertension is based on the average of several accurate readings taken on different days, usually confirmed with home or 24-hour monitoring. One high number is a prompt to measure again properly, not a diagnosis.
Mean arterial pressure (MAP) is the average pressure during one heartbeat and reflects how well organs are being perfused; it is estimated as diastolic plus one-third of the pulse pressure. Pulse pressure is simply systolic minus diastolic. A wide pulse pressure (often above 60 mmHg) can reflect stiffer arteries and is more common with age.
A reading above 180 systolic and/or above 120 diastolic is in the crisis range. Sit down, rest for five minutes and measure again. If it remains that high, contact a doctor promptly. If it comes with chest pain, shortness of breath, severe headache, vision changes, weakness, numbness or difficulty speaking, treat it as an emergency and call your local emergency number immediately.
It can. Readings below about 90/60 mmHg (hypotension) are only a concern if they cause symptoms such as dizziness, light-headedness, fainting or fatigue. For many fit people, low-normal pressure is perfectly healthy. If low readings come with symptoms, discuss them with a doctor.
Use a validated upper-arm monitor. Avoid caffeine, smoking and exercise for 30 minutes beforehand, empty your bladder, and sit quietly for 5 minutes. Sit with your back supported, feet flat on the floor, legs uncrossed, and your arm resting at heart height. Take two or three readings a minute apart, morning and evening, and record the average. This tool only classifies the numbers you enter; it is not a substitute for that routine or for medical advice.
About the Blood Pressure Calculator
High blood pressure is often called the "silent killer" because it usually has no symptoms, yet it quietly raises the risk of heart attack, stroke, heart failure, kidney disease and dementia. The first step in doing something about it is understanding what your numbers mean. This calculator takes a systolic and diastolic reading, classifies it using the 2017 ACC/AHA categories, and explains the result in plain language — along with mean arterial pressure, pulse pressure, a colour-coded position for each number, and practical, evidence-based guidance.
Understanding the two numbers
Every blood-pressure reading has two parts, measured in millimetres of mercury (mmHg). The systolic value (the top, larger number) is the peak pressure in your arteries as the heart contracts and pumps blood out. The diastolic value (the bottom, smaller number) is the lowest pressure, between beats, while the heart relaxes and refills. Both are important. For decades systolic pressure was emphasised because it predicts cardiovascular events well, especially after middle age, but a raised diastolic pressure matters too, particularly in younger adults. A healthy reading needs both numbers to be in range.
The ACC/AHA blood-pressure categories
This tool applies the thresholds defined by the American College of Cardiology and American Heart Association in 2017. When the systolic and diastolic numbers fall into different bands, the higher category always wins.
| Category | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Normal | Less than 120 | and less than 80 |
| Elevated | 120–129 | and less than 80 |
| Stage 1 hypertension | 130–139 | or 80–89 |
| Stage 2 hypertension | 140 or higher | or 90 or higher |
| Hypertensive crisis | Higher than 180 | and/or higher than 120 |
It is worth knowing that guidelines differ around the world. The European (ESC/ESH) and UK (NICE) definitions set the hypertension threshold a little higher — typically 140/90 in the clinic — so a reading this tool labels "Stage 1" may be described as "high-normal" by a doctor following those guidelines. The categories here are a useful, widely used reference, but your clinician interprets them in the context of where you live and your overall health.
Why a single reading is not a diagnosis
Blood pressure is not a fixed value; it rises and falls constantly. It climbs with physical activity, stress, pain, caffeine, nicotine, a full bladder, talking during measurement, cold, and even the anxiety of being measured (the well-known "white-coat" effect). A single high reading is therefore a prompt to measure again carefully — not proof of hypertension. Clinicians diagnose high blood pressure from the average of several accurate readings taken on different occasions, very often confirmed with home monitoring over a week or with a 24-hour ambulatory monitor. Use this calculator to understand a reading, then build a proper record before drawing conclusions.
Measuring correctly
Garbage in, garbage out: an inaccurate measurement makes any classification meaningless. For a reliable home reading, use a validated upper-arm monitor (wrist and finger devices are less reliable), and avoid caffeine, smoking and exercise for 30 minutes beforehand. Empty your bladder, then sit quietly for five minutes. Sit with your back supported and feet flat on the floor, legs uncrossed, with the cuff on a bare upper arm rested at heart height. Stay silent during the measurement. Take two or three readings a minute apart and use the average, ideally morning and evening over several days.
Mean arterial pressure and pulse pressure
The tool also reports two derived numbers. Mean arterial pressure (MAP) approximates the average pressure across a full cardiac cycle and reflects how well blood is reaching your organs; it is estimated as the diastolic pressure plus one-third of the pulse pressure, with a normal range of roughly 70–100 mmHg. Pulse pressure is the gap between systolic and diastolic. A widening pulse pressure — often above 60 mmHg — tends to reflect stiffer, less elastic arteries and becomes more common with age; it is an independent marker of cardiovascular risk in older adults.
What raises blood pressure, and what lowers it
Most high blood pressure is "primary" — it has no single cause but is driven by a mix of genetics, age, excess weight, a high-salt diet, low physical activity, heavy alcohol use, poor sleep and chronic stress. The encouraging part is how responsive it is to change. The most effective lifestyle levers, each shown in trials to lower pressure, are: losing excess weight; following the DASH eating pattern (rich in vegetables, fruit, wholegrains and low-fat dairy, low in saturated fat); cutting salt toward 1,500–2,300 mg of sodium a day; regular aerobic activity (about 150 minutes a week); limiting alcohol; and stopping smoking. These can each lower systolic pressure by several mmHg, and combined they often rival a single medication. Because the relationship between pressure and risk is continuous, even a 5–10 mmHg reduction meaningfully cuts the long-term chance of stroke and heart attack.
When it is an emergency
A reading over 180/120 mmHg is a hypertensive crisis. Rest and re-measure; if it stays that high, seek medical advice promptly. If it is accompanied by chest pain, breathlessness, a severe headache, back pain, vision changes, confusion, weakness, numbness or trouble speaking, this may signal organ damage in progress — call emergency services without delay.
Important limitations
This calculator classifies the numbers you enter against published thresholds; it cannot account for your individual cardiovascular risk, medications, pregnancy, kidney function or other conditions, all of which change how a reading should be interpreted and what target is right for you. It is an educational aid, not a diagnosis, and you should never start, stop or adjust blood-pressure medication based on it. Use it to understand your numbers and to have a better-informed conversation with a qualified healthcare professional.