Blood pressure is the force of blood pushing on the walls of your blood vessels as your heart pumps. A reading has two numbers, like 124/78. You say it as "124 over 78."
The top number
The top number is called systolic (sis-TAH-lik). It shows the pressure when your heart squeezes and pushes blood out.
The bottom number
The bottom number is called diastolic (dye-uh-STAH-lik). It shows the pressure when your heart relaxes between beats.
Both numbers are measured in "millimeters of mercury," written as mm Hg. You will see that on your cuff and in your app.
The blood pressure categories
The American Heart Association uses these categories for adults. Only one number has to be in a higher range for you to be in that category.
| Category | Top number | Bottom number | |
|---|---|---|---|
| Normal | Less than 120 | and | Less than 80 |
| Elevated | 120–129 | and | Less than 80 |
| Stage 1 high blood pressure | 130–139 | or | 80–89 |
| Stage 2 high blood pressure | 140 or higher | or | 90 or higher |
| Severe high blood pressure | Higher than 180 | and/or | Higher than 120 |
Source: American Heart Association, based on the 2025 national guideline.
This table helps you understand your numbers. It is not a diagnosis. Your doctor or nurse will look at several readings over time.
Why one reading is not the whole story
Your blood pressure goes up and down all day. Talking, coffee, stress, a full bladder, or rushing can push one reading higher. That is normal. What matters most is your pattern: your average over days and weeks.
That is why the American Heart Association suggests taking two readings, one minute apart, at about the same time each day, and writing down both.
Why it matters if you feel fine
High blood pressure usually has no signs or symptoms. That is why it is often called the "silent killer" (AHA). Nearly half of U.S. adults have high blood pressure, and about 1 in 6 of them do not know it (CDC). Checking is the only way to know.
One small next step
- Write down your last reading, the date, and the time.
- Learn how to take an accurate reading at home.
- Bring your readings to your next visit.
Sources
- American Heart Association: Home Blood Pressure Monitoring
- 2025 AHA/ACC High Blood Pressure Guideline (Hypertension journal)
- CDC: High Blood Pressure Facts
- American Heart Association: Signs and Symptoms of High Blood Pressure
This guide is for education only. It does not replace advice from your healthcare professional.