Reading a BP monitor is simple: the top number is systolic, the bottom is diastolic, and both matter.
For the full breakdown, see our best BP Monitor guide.
Learning how to read a BP monitor takes about ten seconds once you know what the two numbers mean. The real skill is measuring correctly so the numbers are honest in the first place.
What Do The Two Numbers On A BP Monitor Mean?
The first number your monitor shows is your systolic pressure — the force in your arteries when your heart beats and pushes blood out. The second number is your diastolic pressure — the pressure between beats when your heart relaxes and refills. A reading of 118/76 means a systolic of 118 and a diastolic of 76.
Both numbers matter, but they don’t share equal weight. A high systolic alone can trigger a hypertension diagnosis, and so can a high diastolic on its own. The American Heart Association’s official categories treat either number as the deciding factor.
Blood Pressure Categories: Where Do Your Numbers Land?
| Category | Systolic (Top Number) | Diastolic (Bottom Number) |
|---|---|---|
| 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 |
| Crisis (See Doctor Now) | Higher than 180 | And/or higher than 120 |
A single high reading doesn’t mean you have hypertension. Sustained patterns matter far more than one bad number.
How To Get An Accurate Reading Every Time
The most common reason for confusing or alarming BP readings is poor measuring technique. The cuff goes on a bare upper arm, positioned just above the elbow bend.
Preparation matters just as much as position. Avoid smoking, caffeinated drinks, alcohol, or exercise for 30 minutes beforehand, and empty your bladder first.
Common mistakes that ruin readings include:
- Talking or moving during the measurement
- Using the wrong cuff size for your arm
- Placing the cuff over clothing instead of bare skin
- Letting your arm hang below heart level
The specific compatibility details live in each device’s manual, so check the manufacturer’s support page before buying.
When Should A Reading Send You To The ER?
You have enough to act on now: read the top number, read the bottom number, check them against the categories, and measure correctly every time so those numbers are trustworthy.
FAQs
Is the top or bottom number on a blood pressure monitor more important?
What should you do if your home monitor shows a high reading?
Why do home blood pressure readings differ from the doctor’s office?
References & Sources
- American Heart Association. “Understanding Blood Pressure Readings.” Official source for the BP categories table.
- American Heart Association. “How to Measure Your Blood Pressure.” Official guidance for accurate measurement technique.
- Andon (iHealth). UA-767FAM Digital Blood Pressure Monitor Manual. Notes app compatibility is model-specific.