Blood Pressure Calculator
Type your reading to see which American Heart Association category it falls in, where it sits on the chart, and the average of several readings.
This is not a diagnosis. It shows which category a reading falls in. Only a doctor or other medical professional can confirm high blood pressure, usually from several readings.
Home monitors show the top number first, then the bottom one, often as SYS and DIA. Most show mmHg; a few show kPa.
Most monitors show it too. It's listed for your records; it doesn't change the category.
Add readings from different days and times to see your average. Typed in mmHg, top number first.
How your reading is sorted
Your numbers, step by step. Each number gets a band; the higher band wins.
- 1
Top number
128 → Elevated
- 2
Bottom number
82 → Stage 1
- 3
Higher band wins
Stage 1
- 4
Two extra numbers
PP 128 − 82 = 46
MAP ≈ 97
Read more: the categories, a worked example and how to measure
A blood pressure reading has two numbers. The top number (systolic) is the pressure in your arteries when your heart beats; the bottom number (diastolic) is the pressure between beats. This page places a reading in the American Heart Association (US) categories and shows a few extra numbers. It is general information, not a diagnosis: only a doctor or other medical professional can confirm high blood pressure.
The formula
Category = the higher of (the top number's band) and (the bottom number's band)
Pulse pressure = top number − bottom number
Mean arterial pressure ≈ bottom number + (top number − bottom number) ÷ 3
mmHg = kPa × 7.50062
Each number is rounded to a whole mmHg first, as home monitors show it. An average of several readings is rounded the same way before it gets a category.
Worked example
A reading of 128/82 mmHg. The top number, 128, is in the Elevated band (120–129). The bottom number, 82, is in the Stage 1 band (80–89). The higher of the two is Stage 1, so the reading sits in Stage 1 hypertension.
Pulse pressure is 128 − 82 = 46 mmHg. Mean arterial pressure is 82 + 46 ÷ 3 = 82 + 15.33 = 97.33, about 97 mmHg. In kPa the reading is 128 ÷ 7.50062 = 17.07 and 82 ÷ 7.50062 = 10.93, so about 17.1/10.9 kPa.
For an average, take three readings of 132/84, 128/80 and 124/78. The top numbers add up to 384, and 384 ÷ 3 = 128. The bottom numbers add up to 242, and 242 ÷ 3 = 80.67, which rounds to 81. The average, 128/81, is Stage 1 because of the bottom number.
American Heart Association (US) categories
| Category | Top number, mmHg | Bottom number, 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 |
| Severe hypertension (no symptoms) | higher than 180 | and/or | higher than 120 |
| Hypertensive emergency (with symptoms) | higher than 180 | and/or | higher than 120 |
Severe hypertension and a hypertensive emergency use the same numbers; the difference is symptoms. The American Heart Association says: if your reading is higher than 180 and/or higher than 120, wait one minute and take it again. If it's still that high and you have no other symptoms, contact your healthcare professional. If you have chest pain, shortness of breath, back pain, numbness, weakness, a change in vision or difficulty speaking, call your local emergency number (911 in the US).
In kPa, the main cut-offs are about 16.0, 17.3, 18.7 and 24.0 kPa for the top number, and 10.7, 12.0 and 16.0 kPa for the bottom number. This calculator always changes kPa to mmHg before choosing the category. Categories checked on 13 October 2026.
Other countries' guidelines use somewhat different thresholds, and some count home readings differently from clinic readings. Follow your own doctor's advice about what your numbers mean for you.
Taking a good reading
- Sit quietly for a few minutes first, back supported and feet flat on the floor, with your arm resting at heart level.
- Use a cuff that fits your upper arm, on bare skin. Don't talk during the reading.
- Avoid caffeine, smoking and exercise just before you measure, and empty your bladder.
- Take two or three readings a minute apart, and measure at the same times each day. Blood pressure changes through the day, so one reading doesn't tell the whole story.
- Very low readings can matter too, especially if you feel dizzy or faint. Tell your doctor.
Sources
- Categories and the severe and emergency advice: American Heart Association, Understanding Blood Pressure Readings, checked 13 October 2026.
This calculator gives general information, not medical advice, and it can't diagnose high or low blood pressure. Talk to your doctor about your readings.
Common questions
What do the two numbers in a blood pressure reading mean?
The top number (systolic) is the pressure in your arteries when your heart beats. The bottom number (diastolic) is the pressure between beats, when your heart rests. Both are in millimetres of mercury (mmHg). A reading of 128/82 is said as "128 over 82".
Is 128/82 high blood pressure?
In the American Heart Association (US) categories, a top number of 128 is Elevated (120–129) but a bottom number of 82 is in the Stage 1 range (80–89). When the two numbers fall in different categories, the higher one applies, so 128/82 sits in Stage 1 hypertension. One reading isn't a diagnosis: only a doctor or other medical professional can confirm high blood pressure, usually from several readings.
What blood pressure is an emergency?
The American Heart Association says a reading higher than 180 and/or higher than 120 is severe. Wait one minute and take it again. If it's still that high and you have no other symptoms, contact your healthcare professional. If you also have chest pain, shortness of breath, back pain, numbness, weakness, a change in vision or difficulty speaking, call your local emergency number (911 in the US).
How do I work out my average blood pressure?
Add up all the top numbers and divide by how many readings you have, then do the same for the bottom numbers. For 132/84, 128/80 and 124/78 that's 384 ÷ 3 = 128 and 242 ÷ 3 = 80.7, so an average of about 128/81. Switch to Advanced to type your readings with dates and times and get the average, the highest and the category of the average.
What are pulse pressure and mean arterial pressure (MAP)?
Pulse pressure is the top number minus the bottom number: 128 − 82 = 46 mmHg. Mean arterial pressure is an estimate of the average pressure over one heartbeat: the bottom number plus a third of the pulse pressure, so 82 + 46 ÷ 3 = 97 mmHg. They're shown for information; doctors read them alongside other things.
How do I change kPa to mmHg?
Multiply kilopascals by 7.50062 to get mmHg, or divide mmHg by 7.50062 to get kPa. So 16 kPa is about 120 mmHg and 80 mmHg is about 10.7 kPa. Tap mmHg or kPa above the boxes and the numbers you've typed are changed for you.
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