This calculator gives general estimates for information only. It does not replace advice from your doctor, pharmacist or another qualified health professional.
Reading your blood pressure
A blood pressure reading has two numbers, in millimeters of mercury (mmHg). The systolic pressure (top number) is the peak when the heart beats; the diastolic pressure (bottom number) is the lowest pressure between beats. A reading of 118/76 means 118 systolic over 76 diastolic. This calculator places your reading in the American Heart Association categories and works out two derived values doctors use.
Blood pressure categories (AHA/ACC)
| Category | Systolic | Diastolic | |
|---|---|---|---|
| Normal | below 120 | and | below 80 |
| Elevated | 120–129 | and | below 80 |
| Stage 1 hypertension | 130–139 | or | 80–89 |
| Stage 2 hypertension | 140 or higher | or | 90 or higher |
| Severe (crisis range) | above 180 | and/or | above 120 |
When the two numbers fall in different categories, the higher one counts. A single reading is not a diagnosis: hypertension is confirmed by repeated measurements, ideally with home or 24-hour monitoring.
Mean arterial pressure and pulse pressure
- Mean arterial pressure (MAP) = diastolic + (systolic − diastolic) ÷ 3. It reflects the average pressure pushing blood into your organs over a whole heartbeat, which lasts longer in diastole. In hospitals, a MAP of at least 65 mmHg is the usual minimum to keep organs well supplied.
- Pulse pressure = systolic − diastolic. Around 40 mmHg is typical. Above 60 mmHg, it often reflects stiff arteries, common after 60.
Worked example: 118/76
- Category: normal, since 118 is below 120 and 76 below 80.
- MAP: 76 + (118 − 76) ÷ 3 = 76 + 14 = 90 mmHg.
- Pulse pressure: 118 − 76 = 42 mmHg.
MAP at other systolic readings (diastolic 76)
| Systolic | MAP | Pulse pressure |
|---|---|---|
| 100 | 84 | 24 |
| 120 | 91 | 44 |
| 140 | 97 | 64 |
| 160 | 104 | 84 |
| 180 | 111 | 104 |
How to measure at home
- Sit for five minutes, back supported, feet flat, arm resting at heart level.
- Use a validated upper-arm cuff of the right size; avoid caffeine, smoking and exercise for 30 minutes before.
- Take two readings one minute apart, morning and evening, for a week, and share the average with your doctor.
If a reading is above 180/120 mmHg, rest and measure again. With chest pain, shortness of breath, weakness, trouble speaking or vision changes, call 911.