What the two numbers mean
The top number, systolic, is the pressure while your heart pushes blood out. The bottom number, diastolic, is the pressure between beats, while the heart refills. Both matter: a high reading in either one puts you in the higher category.
The categories
- Normal: under 120 and under 80
- Elevated: 120–129 and under 80
- Stage 1: 130–139 or 80–89
- Stage 2: 140 or more, or 90 or more
- Crisis: over 180 or over 120 — get help immediately
Worked example
A reading of 128/82 falls into stage 1, because the bottom number is 80 or above even though the top number is under 130. Pulse pressure is 46 mmHg and mean arterial pressure is 97 mmHg, both in the usual range.
Measuring it properly
- Sit still for five minutes first, feet flat, back supported, arm resting at heart height.
- No coffee, cigarettes or exercise for half an hour before.
- Take two or three readings a minute apart and use the average. A single high reading proves very little.
An important caveat
- This tool sorts a reading into the published categories. It is not a diagnosis, and no website can replace a doctor.
- Blood pressure moves all day. Diagnosis is based on readings taken on several different days, often at home.
- If you take medication, keep taking it and discuss any change with the doctor who prescribed it.
Frequently asked questions
What is a normal blood pressure?
Below 120 systolic and below 80 diastolic is normal for most adults. 120–129 over under 80 is called elevated, and 130/80 or above is stage 1 high blood pressure.
Which number is more important?
Both are used, and the higher category wins. In people over 50 the systolic number usually carries more weight, because arteries stiffen with age.
What is pulse pressure?
The gap between the two numbers. Around 40 to 60 mmHg is typical; a much wider gap in older adults can point to stiff arteries and is worth mentioning to a doctor.