Blood Pressure Category Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
Blood pressure category is determined from the systolic and diastolic pressures: optimal below 120/80 mmHg, normal between 120-129/80-84, high normal between 130-139/85-89, then hypertension from 140/90 mmHg (grade 1), 160/100 (grade 2), or 180/110 (grade 3, severe).
Explanation
Blood pressure is measured with two numbers: systolic pressure (the higher one, measured when the heart contracts) and diastolic pressure (the lower one, measured between beats). The European classification (ESC/ESH), still widely used in clinical practice in France, defines six categories, from optimal to severe hypertension (grade 3). One important point that's often misunderstood: the category used is always the higher of the two readings, never an average or combination of the two. A reading of 130/70 mmHg, for example, is classified «Normale haute» (high normal) purely because of the systolic pressure (130), even though the diastolic pressure (70) would fall in the optimal category on its own — it's the more unfavorable of the two readings that determines the overall category. An equally important point: a single reading, however accurate, can never diagnose hypertension. Blood pressure naturally varies throughout the day, under the effect of stress, recent physical activity, or even simply the presence of a healthcare professional ("white coat effect"). A diagnosis of hypertension relies on repeated measurements, taken under proper conditions (at rest, seated, for at least 5 minutes), or even on 24-hour ambulatory monitoring or home self-measurement over several days — the only ways to confirm a sustained elevation rather than a one-off spike.
Example: a reading of 130/70 mmHg
Inputs
Systolic pressure: 130 mmHg. Diastolic pressure: 70 mmHg.
Calculation
The systolic pressure (130) falls in the «Normale haute» (high normal) range (130-139), while the diastolic pressure (70) would fall in the «Optimale» (optimal) range on its own. The higher of the two readings determines the final category.
Result
This reading is classified «Normale haute» (high normal), because of the systolic pressure.
Frequently asked questions
Does one elevated reading mean I have hypertension?
No, not necessarily. Blood pressure naturally varies throughout the day and can be temporarily elevated by stress, recent physical exertion, or anxiety linked to the appointment itself (the "white coat effect"). A diagnosis of hypertension relies on repeated measurements taken under proper conditions, or on home self-measurement over several days, not on a single reading.
Why does the category use the higher reading rather than an average?
Because elevated systolic and diastolic readings each reflect a significant cardiovascular risk on their own, even when the other value stays normal — this is particularly common in older adults, whose systolic pressure often rises more than their diastolic pressure. Using the more unfavorable reading avoids underestimating a real risk that an average would mask.
What should I do if my result indicates hypertension?
This calculator gives an informational classification, not a medical diagnosis. If your blood pressure regularly falls in the hypertension categories, or if a single reading is very high (grade 3, from 180/110 mmHg), see a healthcare professional: only they can confirm a diagnosis with repeated measurements and assess whether treatment or monitoring is needed.