Blood Pressure Calculator
Enter your blood pressure reading to find your category using the American Heart Association (AHA) 2017 guidelines.
Blood Pressure Categories (AHA 2017)
| Category | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Normal | < 120 | < 80 |
| Elevated | 120 – 129 | < 80 |
| High BP Stage 1 | 130 – 139 | 80 – 89 |
| High BP Stage 2 | ≥ 140 | ≥ 90 |
| Hypertensive Crisis | > 180 | > 120 |
The AHA revised its guidelines in 2017, lowering the threshold for Stage 1 hypertension from 140/90 to 130/80 mmHg. Classification uses the higher of the two categories when systolic and diastolic place you in different categories.
Understanding Your Numbers
Systolic pressure is the force exerted on artery walls when the heart contracts and pumps blood. It is the upper (larger) number in a reading such as 120/80. Elevated systolic pressure is the most common form of hypertension in adults over 50.
Diastolic pressure is the force on artery walls when the heart relaxes between beats. It is the lower number. Elevated diastolic pressure is more common in younger adults and contributes independently to cardiovascular risk.
A single elevated reading does not necessarily indicate hypertension. Blood pressure fluctuates throughout the day due to activity, stress, caffeine, and posture. Hypertension is diagnosed based on multiple readings on separate occasions. The most accurate readings are taken after 5 minutes of rest, seated, with feet flat on the floor.
How to Get an Accurate Reading
1. Sit quietly for 5 minutes before measuring. Avoid caffeine, exercise, and smoking for 30 minutes beforehand.
2. Sit with your back supported, feet flat on the floor, and arm at heart level. Rest your arm on a flat surface.
3. Use a validated upper-arm cuff monitor. Wrist monitors are less accurate.
4. Take two readings 1–2 minutes apart and record the average. Take readings at the same time each day for the most useful trend data.
5. Record readings in a log — your doctor needs multiple readings over time, not just one measurement.
Frequently Asked Questions
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Normal blood pressure is less than 120/80 mmHg. Readings consistently below this threshold indicate a healthy cardiovascular system. The first number (systolic) measures pressure during heartbeats; the second (diastolic) measures pressure between beats. Optimal BP for long-term cardiovascular health is generally considered to be around 115/75.
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Systolic blood pressure (the top number) is the pressure in your arteries when your heart beats and pumps blood — the peak pressure in each cycle. Diastolic blood pressure (the bottom number) is the pressure when your heart is at rest between beats — the minimum pressure. Both numbers matter: elevated systolic BP is the most common form of hypertension in older adults, while elevated diastolic BP is more concerning in younger adults.
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High blood pressure (hypertension) has many contributing factors: excess sodium intake, insufficient physical activity, obesity, smoking, high alcohol consumption, stress, sleep apnoea, family history, and age. In most cases it develops gradually over years with no single identifiable cause ("primary" or "essential" hypertension). Secondary hypertension from kidney disease, thyroid disorders, or certain medications is less common but worth investigating.
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Evidence-based lifestyle changes include: reducing sodium to under 2,300 mg/day (ideally 1,500 mg), regular aerobic exercise (150 min/week of moderate intensity), maintaining a healthy weight, limiting alcohol to 1–2 drinks/day, not smoking, eating a DASH diet (rich in fruits, vegetables, whole grains, low-fat dairy), and reducing chronic stress. Each of these changes can reduce systolic BP by 4–12 mmHg.
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If your reading is consistently 130/80 or above on multiple occasions, consult a healthcare provider. A reading above 180/120 (hypertensive crisis) requires immediate medical attention, especially if accompanied by chest pain, shortness of breath, visual changes, or severe headache. A single elevated reading is not necessarily cause for alarm — white coat hypertension (elevated readings at the doctor's office from anxiety) is common — but persistent elevation should be evaluated.
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Slightly low blood pressure (below 120/80 but above ~90/60) is generally healthy, especially in younger and fitter people. Blood pressure below 90/60 (hypotension) can cause dizziness, fainting, and in severe cases, inadequate blood flow to vital organs. Sudden drops in BP on standing (orthostatic hypotension), which causes lightheadedness when rising, are common in older adults and should be evaluated if persistent.