Systolic Blood Pressure

Measured in mmHg

The top blood pressure number — the pressure in your arteries during a heartbeat — which varies a lot from reading to reading, so a single measurement is a poor estimate on its own.

What it is

Systolic blood pressure is the top number in a reading, reflecting the pressure inside your arteries at the moment your heart contracts and pushes blood out. It moves around a great deal — time of day, stress, caffeine, talking, cuff size, arm position, and the 'white coat' effect of being in a clinic can all shift it — so it's read as a pattern across repeated measurements rather than judged from any one number. It's usually reviewed together with your diastolic number and the rest of your health picture. Because technique matters so much, readings taken with a poorly fitting cuff or an unsupported arm may not reflect your usual pressure.

Typical range

  • Adultsunder 120 mmHg

Source · 2025 AHA/ACC (2025)

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

  • Am I measuring my blood pressure in a way that gives you readings you can trust — cuff size, arm position, timing?
  • Looking at my readings as a trend rather than one number, what pattern do you see?
  • Would home readings over time, or something like ambulatory monitoring, give you a more useful picture than clinic readings?