High blood pressure rarely causes symptoms but is the leading risk factor for stroke and heart attack worldwide. The 2017 American guideline lowered the threshold for hypertension to 130/80 mmHg; European and many other guidelines still use 140/90.
How to use the Blood Pressure Calculator
- Reading 1 – systolic
- Reading 1 – diastolic
- Reading 2 – systolic (0 to skip)
- Reading 2 – diastolic (0 to skip)
- Reading 3 – systolic (0 to skip)
- Reading 3 – diastolic (0 to skip)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Sit quietly for 5 minutes with your back supported, feet flat and arm at heart level, then take two or three readings a minute apart. Enter up to three readings; the calculator averages them and classifies the result. A reading above 180/120 needs urgent medical attention.
Blood pressure categories (ACC/AHA 2017)
| Category (ACC/AHA 2017) | Systolic (mmHg) | Diastolic (mmHg) | |
|---|---|---|---|
| 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 |
| Hypertensive crisis | above 180 | and/or | above 120 |
Inputs explained
| Field | What to enter |
|---|---|
| Reading 1 – systolic | In mmHg |
| Reading 1 – diastolic | In mmHg |
| Reading 2 – systolic (0 to skip) | In mmHg |
| Reading 2 – diastolic (0 to skip) | In mmHg |
| Reading 3 – systolic (0 to skip) | In mmHg |
| Reading 3 – diastolic (0 to skip) | In mmHg |
What each result means
- Average systolic = ([Reading 1 – systolic] + [Reading 2 – systolic (0 to skip)] + [Reading 3 – systolic (0 to skip)])÷(1 + ([Reading 2 – systolic (0 to skip)] > 0) + ([Reading 3 – systolic (0 to skip)] > 0))
- Average diastolic = ([Reading 1 – diastolic] + [Reading 2 – diastolic (0 to skip)] + [Reading 3 – diastolic (0 to skip)])÷(1 + ([Reading 2 – diastolic (0 to skip)] > 0) + ([Reading 3 – diastolic (0 to skip)] > 0))
- Mean arterial pressure = [Average diastolic] + ([Average systolic] – [Average diastolic])÷3
- Pulse pressure = [Average systolic] – [Average diastolic]
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Category from the higher of the systolic and diastolic categories
MAP = DBP + (SBP − DBP) ÷ 3
Pulse pressure = SBP − DBP
Worked example
Inputs — Reading 1 – systolic: 128 mmHg; Reading 1 – diastolic: 82 mmHg; Reading 2 – systolic (0 to skip): 126 mmHg; Reading 2 – diastolic (0 to skip): 80 mmHg; Reading 3 – systolic (0 to skip): 0 mmHg; Reading 3 – diastolic (0 to skip): 0 mmHg.
Results — Average systolic = 127 mmHg; Average diastolic = 81 mmHg; Blood pressure category (ACC/AHA) = Stage 1 hypertension; Category (ESC/ESH 140/90 guideline) = Normal; Mean arterial pressure = 96 mmHg; Pulse pressure = 46 mmHg.
Key terms
- Systolic
- Pressure when the heart contracts (top number).
- Diastolic
- Pressure between beats (bottom number).
- Pulse pressure
- Difference between systolic and diastolic.
Frequently asked questions
What is normal blood pressure?
Below 120/80 mmHg.
What blood pressure is too high?
130/80 or more is hypertension in US guidelines (140/90 in many others); above 180/120 is a crisis.
Why should I take several readings?
Blood pressure varies minute to minute; averaging gives a truer picture.
Is low blood pressure a problem?
Only if it causes symptoms such as dizziness or fainting.