About the Blood Pressure Calculator
This blood pressure calculator tells you what your reading means. Enter the top number (systolic — the pressure when your heart beats) and the bottom number (diastolic — the pressure between beats) from any home monitor or clinic reading, and it places the result in the American Heart Association / American College of Cardiology categories: normal, elevated, stage 1 hypertension, stage 2 hypertension, or the severe range that needs urgent attention.
It also works out your pulse pressure (the gap between the two numbers) and mean arterial pressure (the average pressure driving blood to your organs), which doctors use as extra indicators of artery stiffness and circulation. The chart compares your reading with the key thresholds.
When the two numbers fall in different categories, the higher category applies. A single reading is not a diagnosis: blood pressure varies through the day, so doctors base decisions on the average of several readings taken on different days, ideally seated after five minutes of rest.
How to use the blood pressure calculator
- 1Sit quietly for five minutes with your back supported and feet flat.
- 2Take a reading with your arm supported at heart level.
- 3Enter the systolic (top) and diastolic (bottom) numbers.
- 4Read your category, pulse pressure and mean arterial pressure.
- 5Repeat on several days and discuss the average with your doctor.
Formula and method
The category is chosen from the AHA/ACC adult thresholds, first introduced in the 2017 guideline and kept in later updates. Each number is classified separately and the higher of the two categories is reported — so 125/85 is stage 1 because the diastolic value is 80–89, even though the systolic value alone would only be elevated. Readings above 180 systolic or 120 diastolic are flagged as the severe range.
Pulse pressure is simply the difference between the two numbers. Mean arterial pressure uses the standard clinical approximation that the heart spends about two-thirds of each cycle in diastole, so the average pressure is the diastolic value plus one-third of the pulse pressure.
- SBP
- Systolic blood pressure, mmHg (top number)
- DBP
- Diastolic blood pressure, mmHg (bottom number)
- MAP
- Mean arterial pressure, mmHg
Worked examples
Reading of 128/82
The systolic 128 alone would be “elevated”, but the diastolic 82 is in the 80–89 band, so the reading counts as stage 1 hypertension. Pulse pressure is 128 − 82 = 46 mmHg and MAP is 82 + 46 ÷ 3 ≈ 97.3 mmHg.
Reading of 118/76
Both numbers are below the normal limits of 120 and 80. The pulse pressure is 42 mmHg and MAP is 76 + 42 ÷ 3 = 90 mmHg.
Reading of 152/88
A systolic reading of 140 or more is stage 2 regardless of the diastolic value. The pulse pressure of 64 mmHg is on the wide side, and MAP is 88 + 64 ÷ 3 ≈ 109.3 mmHg.
Frequently asked questions
What is a normal blood pressure?+
For adults, normal is a systolic pressure below 120 mmHg and a diastolic pressure below 80 mmHg. 120–129 with a diastolic below 80 is “elevated”, and 130/80 or higher is classed as hypertension under the AHA/ACC guideline.
Does normal blood pressure change with age?+
The adult categories are the same at every age from 18 upward. Blood pressure does tend to rise with age, especially systolic pressure, but that makes high readings more common rather than normal. Children and teens are assessed with percentile charts instead.
Which number matters more, systolic or diastolic?+
Both matter. After about age 50, systolic pressure is the stronger predictor of heart attack and stroke risk, but a high diastolic value alone is enough to place you in a hypertension category.
What blood pressure is dangerously high?+
A reading above 180 systolic and/or 120 diastolic is in the severe range. Re-check after a few minutes; if it remains that high, contact a doctor right away, and call emergency services if you also have chest pain, shortness of breath, back pain, numbness, weakness, or changes in vision or speech.
Why is my blood pressure higher at the doctor’s office?+
Many people have “white coat” hypertension — readings pushed up by the stress of the visit. Home monitoring or 24-hour ambulatory monitoring helps show your usual level; home averages of 130/80 or higher are generally treated as hypertension.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.