How to use the blood pressure calculator
- Enter your Systolic (top) number, the higher of the two readings, as a whole number in mmHg.
- Enter your Diastolic (bottom) number, the lower one.
- Read the category and explanation. The table below highlights your row, and the tiles show pulse pressure and mean arterial pressure.
How the categories are decided
The tool uses the adult categories from the 2017 ACC/AHA guideline, which the 2025 AHA/ACC guideline kept unchanged. Normal is below 120 and below 80. Elevated is 120 to 129 and below 80. Stage 1 is 130 to 139 or 80 to 89. Stage 2 is 140 or higher or 90 or higher. A hypertensive crisis is higher than 180 and/or higher than 120, as described by the American Heart Association. If the two numbers fall in different categories, the higher one applies.
A reading below 90 systolic or below 60 diastolic that is not high is labeled Low, following the common cutoff described by the NHS. Pulse pressure is systolic minus diastolic, and mean arterial pressure is (systolic + 2 × diastolic) / 3.
Worked example
The starting inputs are 118/76 mmHg. Systolic 118 is below 120 and diastolic 76 is below 80, so the category is Normal. Pulse pressure is 118 - 76 = 42 mmHg, and mean arterial pressure is (118 + 2 × 76) / 3 = 90 mmHg. For a mixed reading such as 126/82, the systolic number is Elevated but the diastolic number is Stage 1, so the result is Stage 1.
Limits and edge cases
A single reading is not a diagnosis, and treatment depends on repeated readings and your overall heart risk. The CDC describes high blood pressure as consistently at or above 130/80. The calculator needs whole numbers, a systolic from 50 to 300 and a diastolic from 30 to 200, with the top number higher than the bottom. At exactly 180 systolic or 120 diastolic the AHA wording is still stage 2, but some sources already call it a crisis, so the result adds a note to rest and retest. Related tools: the BMI calculator, the cholesterol ratio calculator and the heart rate zones calculator.
Frequently asked questions
Is 120/80 normal blood pressure?
Not under the American Heart Association categories. Normal means below 120 systolic and below 80 diastolic, so 120/80 lands in stage 1 hypertension, because a diastolic of 80 is in the 80 to 89 range. When the two numbers fall in different categories, the higher category applies.
What blood pressure is dangerously high?
The AHA calls readings higher than 180 systolic and/or higher than 120 diastolic a hypertensive crisis. Rest and test again. If it stays that high, contact your clinician right away, and call 911 if you also have chest pain, shortness of breath, back pain, numbness or weakness, vision changes or trouble speaking.
Does one high reading mean I have high blood pressure?
No. Blood pressure changes through the day, and diagnosis rests on repeated readings. The 2025 AHA/ACC guideline recommends home monitoring to help confirm an office diagnosis. Sit quietly for 5 minutes with your back supported and feet flat, then take two readings a minute apart, morning and evening.
Do the blood pressure categories change with age?
No. The categories apply to all adults 18 and over, and the treatment goal for most adults is below 130/80. Children and teens are judged against percentile charts, which this tool does not use.
What counts as low blood pressure?
There is no single AHA cutoff, but a reading below 90/60 is commonly called low. It causes no trouble for some people. Dizziness, fainting, blurred vision or weakness are reasons to talk to a clinician.
Sources: AHA, Understanding Blood Pressure Readings; 2025 AHA/ACC high blood pressure guideline; CDC; NHS, low blood pressure; AHA/AMA self-measured blood pressure statement. General information, not medical advice.