Most home blood pressure monitors display three numbers. Many people know roughly what blood pressure means but aren't sure what each number on the screen represents — or which one to pay attention to. Here's a plain-language guide.
The three numbers on your monitor
Systolic (the top, larger number)
This is the pressure in your arteries when your heart contracts and pushes blood out. It's usually the larger of the two blood pressure numbers — for example, the 118 in 118/76 mmHg.
Systolic pressure is the number most closely watched by doctors for cardiovascular risk, especially in people over 50, because it tends to rise with age and arterial stiffness even when diastolic stays stable.
Diastolic (the bottom, smaller number)
This is the pressure when your heart relaxes between beats. In 118/76 mmHg, it's the 76. Diastolic pressure tends to matter more in younger adults; in older adults, systolic is generally the more informative number.
Pulse (heart rate)
Most monitors also show your pulse in beats per minute (bpm). This is a separate measurement from blood pressure — having a high heart rate doesn't automatically mean high blood pressure, and vice versa. A resting pulse of 60–100 bpm is considered normal for adults, though highly trained athletes may be well below 60.
The unit: mmHg
Blood pressure is measured in millimetres of mercury (mmHg) — a unit inherited from the original mercury manometers used by doctors. It's the universal standard; all readings worldwide use mmHg.
What the categories mean
| Category | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Normal | <120 | <80 |
| Elevated | 120–129 | <80 |
| Stage 1 hypertension | 130–139 | 80–89 |
| Stage 2 hypertension | ≥140 | ≥90 |
| Hypertensive crisis | >180 | >120 |
Source: American Heart Association guidelines, 2017. ESC/ESH guidelines use slightly different thresholds — your doctor will apply whichever is relevant for your region.
What to ignore
A single out-of-range reading. Blood pressure fluctuates throughout the day — stress, caffeine, full bladder, posture and talking during measurement can all shift a reading by 10–20 mmHg. One high result is not a diagnosis. A consistent pattern over days is.
Minor variation between readings. Taking the same reading twice and getting 118/76 and then 122/78 is completely normal. Use the average, and don't chase the lower number.
The most important thing your monitor can tell you isn't today's number — it's the direction your average has been moving over the past two weeks.
When to act immediately
A reading above 180/120 mmHg, especially with symptoms like chest pain, severe headache, or shortness of breath, is a hypertensive crisis. Call emergency services or go to an emergency room. Don't wait to check again.
Track this in BloodSnap. Log systolic, diastolic and pulse in seconds, see your weekly and monthly trend, and know at a glance if your pattern is changing.