Normal blood pressure is a reading below 120/80 mm Hg. That means the top number (systolic) stays under 120 and the bottom number (diastolic) stays under 80. Once either number crosses those thresholds, your blood pressure moves into higher-risk categories that may need attention.
What the Two Numbers Mean
A blood pressure reading gives you two numbers, like 115/75. The top number, systolic pressure, measures the force your blood pushes against your artery walls when your heart beats. The bottom number, diastolic pressure, measures that same force between beats, when your heart is resting. Both numbers matter, and either one being too high or too low can signal a problem.
Blood pressure is measured in millimeters of mercury, written as mm Hg. This unit dates back to the mercury columns used in early blood pressure devices, and it stuck as the standard.
Blood Pressure Categories for Adults
The 2025 guidelines from the American Heart Association and American College of Cardiology break adult blood pressure into four categories:
- Normal: Systolic below 120 and diastolic below 80
- Elevated: Systolic 120 to 129 and diastolic below 80
- Hypertension Stage 1: Systolic 130 to 139 or diastolic 80 to 89
- Hypertension Stage 2: Systolic 140 or higher, or diastolic 90 or higher
Notice the word “or” in the hypertension stages. If just one of your numbers is elevated, that’s enough to place you in a higher category. You don’t need both numbers to be high.
European guidelines use a slightly different system. The 2024 European Society of Cardiology guidelines dropped terms like “normal” and “optimal” entirely for readings below 120/70, because cardiovascular risk rises with every incremental increase in blood pressure, even within that range. Instead, they classify anything below 120/70 as “nonelevated,” 120 to 139 over 70 to 89 as “elevated,” and 140/90 or above as hypertension. The practical takeaway: even a “normal” reading doesn’t mean lower is pointless. Healthy habits still help.
When Blood Pressure Is Too Low
A reading below 90/60 mm Hg is generally considered low blood pressure, or hypotension. On its own, a low number isn’t necessarily a problem. Some people run low naturally and feel perfectly fine. It only becomes a concern when it causes symptoms like dizziness, fainting, blurred vision, or fatigue.
One specific type to know about is orthostatic hypotension, where your blood pressure drops when you stand up from sitting or lying down. If the top number drops by 20 or more, or the bottom number drops by 10 or more, and stays low for longer than three minutes after standing, that qualifies. It’s common in older adults and can increase fall risk.
Why a Single Reading Can Be Misleading
Your blood pressure is not a fixed number. It shifts throughout the day in a predictable pattern: it starts rising a few hours before you wake up, peaks around midday, then drops in the late afternoon and evening. It reaches its lowest point while you sleep. An abnormally high surge in the morning hours has been linked to increased heart disease risk.
Beyond daily fluctuations, the setting where you’re measured matters more than most people realize. About 14% of people have what’s called white coat hypertension, where readings are high at a doctor’s office but normal at home. Another 10% have the opposite pattern, masked hypertension, where office readings look fine but blood pressure runs high during everyday life. Masked hypertension is particularly risky because it often goes undetected. This is why a single reading at your annual checkup doesn’t tell the full story, and why home monitoring or repeated measurements give a much clearer picture.
How to Get an Accurate Reading
Small details in how you measure can swing your reading by 10 to 15 points, enough to push a normal reading into the elevated range or hide a genuinely high one. The CDC recommends a specific routine for reliable results:
- Sit and rest first. Sit in a comfortable chair with your back supported for at least five minutes before taking the reading.
- Position your arm correctly. Rest the arm wearing the cuff on a table at chest height. Letting it hang at your side inflates the number.
- Use bare skin. The cuff should sit snug against your bare arm, not over a sleeve.
- Empty your bladder. A full bladder can raise systolic pressure noticeably.
If you’re monitoring at home, take two or three readings about a minute apart and average them. Measure at the same time each day, ideally morning and evening, for the most consistent tracking.
What Counts as a Hypertensive Crisis
A reading of 180/120 mm Hg or higher is considered a hypertensive crisis. There are two levels. If your reading hits that threshold but you have no other symptoms, it’s classified as urgent. If the same reading comes with signs like chest pain, shortness of breath, vision changes, difficulty speaking, or severe headache, it may indicate organ damage and is classified as an emergency. In either case, a reading that high calls for immediate medical attention.
Blood Pressure in Children
Normal blood pressure in children doesn’t follow the same fixed cutoffs that apply to adults. Instead, it’s evaluated based on the child’s age, sex, and height. The National Institutes of Health publishes percentile-based tables for children ages 1 through 17, where a reading at or above the 95th percentile for their specific age and height group is considered high. This means a blood pressure that’s normal for a tall 12-year-old might be elevated for a shorter 8-year-old. Your child’s pediatrician uses these charts at routine visits to track whether readings are tracking normally over time.