A blood pressure machine displays two large numbers stacked on top of each other, and usually a third smaller number below or beside them. The top number is your systolic pressure, the bottom number is your diastolic pressure, and the third number is your pulse rate. Understanding what these numbers mean, and what counts as normal, takes just a few minutes to learn.
What the Two Main Numbers Mean
The top (larger) number is your systolic pressure. It measures the force of blood against your artery walls when your heart contracts and pushes blood out. The bottom number is your diastolic pressure, which measures the residual pressure in your arteries between beats, when your heart is briefly at rest. Both numbers are displayed in millimeters of mercury, abbreviated as mm Hg, though most home machines don’t show the unit on screen.
A reading of 118/76, for example, means your systolic pressure is 118 and your diastolic is 76. You’ll sometimes hear this spoken as “118 over 76.” Both numbers matter. If either one falls into a higher category, the higher category applies to you.
Blood Pressure Categories by the Numbers
The 2025 guidelines from the American Heart Association and American College of Cardiology break blood pressure into four categories:
- Normal: systolic below 120 and diastolic below 80
- Elevated: systolic 120 to 129 and diastolic below 80
- Stage 1 hypertension: systolic 130 to 139 or diastolic 80 to 89
- Stage 2 hypertension: systolic 140 or higher, or diastolic 90 or higher
Notice the word “or” in the hypertension stages. If your top number is 136 but your bottom number is 72, you still fall into stage 1 hypertension because the systolic number qualifies on its own. Always use whichever number places you in the higher category.
A reading of 180/120 or higher is considered a hypertensive crisis. If you see numbers that high along with symptoms like chest pain, severe headache, blurred vision, shortness of breath, or confusion, call 911 immediately.
The Third Number: Your Pulse Rate
Most digital monitors display a heart icon next to a third number. This is your pulse rate in beats per minute. A normal resting heart rate for adults falls between 60 and 100 beats per minute. It’s useful context, but it’s separate from blood pressure. A normal pulse doesn’t guarantee normal blood pressure, and vice versa.
Common Symbols on the Screen
Digital monitors use a few icons beyond the numbers themselves. An irregular heartbeat symbol (often a heart with a jagged line) appears when the machine detects an irregular rhythm two or more times during a reading. This doesn’t necessarily mean something is wrong, but if it shows up repeatedly across multiple sessions, it’s worth mentioning to your doctor.
A movement error symbol means you shifted your arm or body during the measurement, which can throw off the reading. Retake it after sitting still for a minute. A battery icon with a low indicator means it’s time to swap in fresh batteries. Depleted batteries can affect accuracy, so don’t ignore this one.
How to Get an Accurate Reading
The numbers on your screen are only useful if the reading is taken correctly. Several common factors can skew your results significantly: recent exercise, alcohol or nicotine use, a full bladder, talking during the measurement, crossing your legs, and even a cold room.
To get reliable numbers, sit in a chair with your back supported and both feet flat on the floor. Rest quietly for five minutes before you start. Place your arm on a flat surface like a desk or table so the middle of the cuff sits at heart level. Don’t talk during the reading, and keep your legs uncrossed.
Cuff Size Matters
Using the wrong cuff size is one of the most common sources of inaccurate readings. Four adult cuff sizes are available: small (for arm circumference of 20 to 25 cm), regular (25 to 32 cm), large (32 to 40 cm), and extra-large (40 to 55 cm). Measure around the midpoint of your upper arm with a flexible tape measure to find which size you need. A cuff that’s too small will give you a falsely high reading, and one that’s too large may read falsely low.
Arm Position Changes the Reading
A randomized clinical trial published in JAMA Internal Medicine found that arm position significantly affects results. Guidelines recommend supporting your arm on a desk with the cuff at heart level. Letting your arm hang at your side or holding it up unsupported can add several points to your reading, making your blood pressure look worse than it actually is.
How to Track Your Readings Over Time
A single reading is a snapshot, not a diagnosis. Blood pressure fluctuates throughout the day based on stress, caffeine, activity, and dozens of other variables. What matters is the pattern over time.
The CDC recommends taking your blood pressure at the same time every day. At each session, take at least two readings spaced one to two minutes apart and record all of them in a log. Many digital monitors store recent readings in memory, but keeping a written or app-based log makes it easier to spot trends and share results with your doctor. If you’re monitoring for high blood pressure, your healthcare team may ask you to measure more frequently than someone whose readings are consistently normal.
When you look at your log, pay attention to averages rather than any single reading. One high number after a stressful afternoon doesn’t mean you have hypertension. A pattern of readings consistently above 130/80 over multiple days does.