What do systolic and diastolic numbers mean?

The systolic number (top) is the pressure in your arteries when your heart beats and pumps blood. The diastolic number (bottom) is the pressure between beats when your heart is resting. Blood pressure is written as systolic/diastolic (e.g., 120/80 mmHg).

What is a normal blood pressure reading?

According to the 2017 AHA/ACC guidelines, a normal blood pressure is less than 120 mmHg systolic AND less than 80 mmHg diastolic. Readings above these thresholds are classified as elevated or hypertensive.

What should I do if my reading shows hypertensive crisis?

A reading above 180/120 mmHg is a hypertensive crisis. If you are experiencing chest pain, shortness of breath, back pain, numbness, difficulty speaking, or vision changes, call 911 immediately. If you have no symptoms, wait a few minutes and re-test. If still high, contact your doctor urgently.

Can I rely on a single home reading?

A single reading is not a diagnosis. Blood pressure varies throughout the day due to activity, stress, caffeine, and measurement technique. For accurate assessment, take readings at the same time each day for several days, seated and rested for 5 minutes, and share the average with your doctor.

What causes high blood pressure?

Common causes include a high-sodium diet, physical inactivity, obesity, excessive alcohol, smoking, chronic stress, genetics, and certain medications. Secondary hypertension can result from kidney disease, thyroid disorders, or sleep apnea. Most hypertension has no symptoms - hence its "silent killer" nickname.

Blood Pressure Category Checker - AHA/ACC Guidelines

Category ▲▼	Systolic ▲▼	Diastolic ▲▼
Normal	Less than 120 mmHg	Less than 80 mmHg
Elevated	120–129 mmHg	Less than 80 mmHg
High Blood Pressure - Stage 1	130–139 mmHg	80–89 mmHg
High Blood Pressure - Stage 2	140+ mmHg	90+ mmHg
Hypertensive Crisis	Higher than 180 mmHg	Higher than 120 mmHg

Category ▲▼

Systolic ▲▼

Diastolic ▲▼

Normal

Less than 120 mmHg

Less than 80 mmHg

Elevated

120–129 mmHg

Less than 80 mmHg

High Blood Pressure - Stage 1

130–139 mmHg

80–89 mmHg

High Blood Pressure - Stage 2

140+ mmHg

90+ mmHg

Hypertensive Crisis

Higher than 180 mmHg

Higher than 120 mmHg

Understanding blood pressure readings

Blood pressure is measured in millimeters of mercury (mmHg) and expressed as two numbers: systolic/diastolic. The systolic pressure is measured when your heart beats; the diastolic pressure is measured between beats. For example, 120/80 mmHg means a systolic pressure of 120 and a diastolic pressure of 80.

AHA/ACC blood pressure categories

The 2017 American Heart Association (AHA) and American College of Cardiology (ACC) guidelines define five blood pressure categories for adults. The key change from older guidelines was lowering the hypertension threshold from 140/90 to 130/80 mmHg, reflecting evidence that cardiovascular risk increases significantly above that level.

Tips for an accurate home reading

Sit quietly for 5 minutes before measuring.
Keep your feet flat on the floor, back supported, arm at heart level.
Do not smoke, drink caffeine, or exercise within 30 minutes of measuring.
Take two or three readings, 1 minute apart, and average the results.
Measure at the same time each day (morning and evening).
Record your readings to share with your doctor.

Lifestyle changes to lower blood pressure

DASH diet: rich in fruits, vegetables, whole grains, low-fat dairy, and lean protein; low in sodium and saturated fat.
Reduce sodium: aim for less than 2,300 mg/day; less than 1,500 mg/day if already hypertensive.
Exercise: 150 minutes of moderate-intensity aerobic activity per week.
Limit alcohol: no more than 1 drink/day for women, 2 for men.
Quit smoking: smoking damages blood vessels and raises cardiovascular risk.
Manage stress: chronic stress contributes to elevated blood pressure.

White coat hypertension

Many people experience elevated blood pressure readings at a doctor's office or clinic - a phenomenon called white coat hypertension - due to anxiety about the clinical setting. Readings taken at home in a relaxed environment are often 10–15 mmHg lower than clinic readings and provide a more accurate picture of your baseline blood pressure. If your home readings are consistently normal but clinic readings are elevated, mention this to your doctor; some guidelines now require out-of-office confirmation before diagnosing hypertension.

Pulse pressure

Pulse pressure is the difference between systolic and diastolic readings:

Pulse Pressure = Systolic − Diastolic

A normal pulse pressure is approximately 40 mmHg. A pulse pressure above 60 mmHg is considered wide and is associated with increased risk of cardiovascular events, particularly in older adults (it reflects reduced arterial elasticity). A narrow pulse pressure (below 25 mmHg) can indicate low stroke volume and may warrant evaluation.