THE NUMORIX GUIDE
How to use the Blood Pressure Calculator
Last reviewed September 14, 2026
What this calculator does
The classifier checks the crisis threshold first: systolic >= 180 or diastolic >= 120.
Formula and method
The classifier checks the crisis threshold first: systolic >= 180 or diastolic >= 120. It then checks stage 2 at systolic >= 140 or diastolic >= 90, stage 1 at systolic >= 130 or diastolic >= 80, elevated at systolic 120-129 with diastolic < 80, and otherwise normal.
Variables and inputs
Systolic and diastolic pressure are entered in mmHg. The first number is the pressure when the heart contracts; the second is the pressure between beats. The UI accepts systolic values from 50 to 300 and diastolic values from 30 to 200.
Worked example
For 128/76 mmHg, 128 is below 130 but in the 120-129 band, and 76 is below 80, so the engine returns Elevated. For 140/88, systolic alone reaches the stage 2 threshold, so the result is High Blood Pressure Stage 2.
How to interpret the result
The category is a screening label for one entered reading. The higher category wins when systolic and diastolic values fall in different bands. It is not a diagnosis of hypertension or a substitute for a series of properly taken readings.
Common mistakes to avoid
Enter systolic first and diastolic second, and keep both values in mmHg. Do not average the two numbers or classify a reading from the lower number alone. Rest quietly and use a validated cuff when collecting readings for clinical discussion.
Assumptions and limitations
The engine does not average repeated readings, check cuff size or measurement technique, or account for age, pregnancy, medications, symptoms, or clinical history. At the crisis threshold it displays an emergency recommendation; very high readings, especially with symptoms, require urgent medical attention rather than another calculator result.