Cardiovascular
Blood Pressure Classifier
Check systolic and diastolic blood pressure against American Heart Association categories.
Last reviewed: August 2026
Result
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How this is classified
Categories follow American Heart Association guidance: Normal (below 120/80), Elevated (120-129 systolic, below 80 diastolic), Hypertension Stage 1 (130-139/80-89), Stage 2 (140+/90+), and Hypertensive Crisis (180+/120+, which warrants prompt medical evaluation). Low blood pressure (below 90/60) is flagged separately — it's not part of the AHA hypertension scale, but is worth noting if you experience symptoms alongside it.
Why one reading isn't the full picture
Blood pressure fluctuates through the day and can be elevated temporarily by stress, caffeine, or the anxiety of being measured at a clinic ("white coat effect"). Clinical diagnosis of hypertension typically relies on multiple readings over time, sometimes with home monitoring.
Worked example
Example
A reading of 128/82 mmHg lands in Elevated territory — systolic is under 130 but diastolic (82) has crossed into the range associated with Stage 1. Where systolic and diastolic fall into different categories, the higher category generally applies. A single reading like this isn't a diagnosis; it's a signal to recheck over the following days, ideally at a similar time and after resting quietly for 5 minutes beforehand.
Getting an accurate home reading
- Sit quietly for 5 minutes first, feet flat on the floor, back supported.
- Arm supported at heart height — a hanging or unsupported arm can raise the reading.
- No caffeine, exercise, or smoking in the 30 minutes before measuring.
- Take two readings a minute apart and use the average.
Common mistakes
- Diagnosing from one reading. Guidelines call for readings on multiple occasions before labeling someone hypertensive — this tool classifies a single number, it doesn't diagnose.
- Wrong cuff size. A cuff that's too small for the arm can inflate readings by a meaningful margin.
- Ignoring symptoms because "the number wasn't that high." Category and symptoms are both relevant — severe headache, chest pain, or vision changes warrant care regardless of the exact number.
My systolic and diastolic fall into different categories — which one counts?
The higher category typically applies. A reading of 135/78, for example, is treated as Stage 1 because of the systolic number, even though diastolic is in the normal range.
Is a single high reading an emergency?
Not usually — unless it's in Hypertensive Crisis range (180+/120+) or accompanied by symptoms like chest pain, shortness of breath, or severe headache, in which case seek care promptly.
Why did my reading vary so much between arms?
A modest difference between arms is common; a large or persistent difference is worth mentioning to a healthcare provider, as it can occasionally indicate a vascular issue.
Sources
- American Heart Association. Understanding Blood Pressure Readings.