[Image of blood pressure categories chart]

Data Source & Methodology

This calculator classifies your blood pressure reading based on the authoritative guidelines published by the American Heart Association (AHA) and the American College of Cardiology (ACC).

  • Authoritative Source: 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults.
  • Reference: Circulation. 2018;137:e495–e504.

All calculations and category classifications are based strictly on the formulas and data provided by this source. The logic is applied in a hierarchical order, checking for the most severe category first.

The Formula (Category Logic)

Blood pressure is not calculated with a single formula but classified using a set of logical conditions. Let $S$ represent Systolic pressure and $D$ represent Diastolic pressure.

The category is determined by checking the following conditions in order, from highest risk to lowest:

$$ \text{Category} = \begin{cases} \text{Hypertensive Crisis} & \text{if } S > 180 \text{ or } D > 120 \\ \text{High BP (Stage 2)} & \text{if } S \ge 140 \text{ or } D \ge 90 \\ \text{High BP (Stage 1)} & \text{if } (130 \le S \le 139) \text{ or } (80 \le D \le 89) \\ \text{Elevated} & \text{if } (120 \le S \le 129) \text{ and } D < 80 \\ \text{Normal} & \text{if } S < 120 \text{ and } D < 80 \end{cases} $$

Note: If your reading falls into two different categories (e.g., $S$ is 'Stage 1' but $D$ is 'Stage 2'), the higher (more severe) category is assigned.

Glossary of Variables

Systolic Blood Pressure ($S$)
The "top number" in a blood pressure reading, measured in millimeters of mercury (mm Hg). It indicates the maximum pressure your blood exerts against your artery walls when your heart beats.
Diastolic Blood Pressure ($D$)
The "bottom number" in a reading (mm Hg). It indicates the pressure in your arteries when your heart is at rest between beats.
Blood Pressure Category
The classification of your reading, which helps you and your healthcare provider understand your risk for heart disease and stroke.

How It Works: A Step-by-Step Example

Let's walk through a practical example to see how the logic is applied.

  • Input Values:
    • Systolic Pressure ($S$) = 135 mm Hg
    • Diastolic Pressure ($D$) = 85 mm Hg
  • Step-by-Step Evaluation:
    1. Is it a Hypertensive Crisis? (Is $S > 180$ or $D > 120$?)
      No. (135 is not > 180, and 85 is not > 120).
    2. Is it High BP (Stage 2)? (Is $S \ge 140$ or $D \ge 90$?)
      No. (135 is not $\ge$ 140, and 85 is not $\ge$ 90).
    3. Is it High BP (Stage 1)? (Is $130 \le S \le 139$ or $80 \le D \le 89$?)
      Yes. (135 is between 130-139) AND (85 is between 80-89).
  • Final Result: The reading is classified as High Blood Pressure (Stage 1).

Frequently Asked Questions (FAQ)

What do my blood pressure numbers mean?

Your blood pressure is recorded as two numbers: systolic (top) and diastolic (bottom). Systolic measures the pressure as your heart beats, while diastolic measures the pressure as it rests. Both are important indicators of your cardiovascular health.

Is this calculator a substitute for medical advice?

No. This calculator is an informational tool, not a medical diagnosis. A single reading does not define your health. Only a qualified healthcare professional can diagnose high blood pressure (hypertension) and create a treatment plan based on your complete health profile.

When should I see a doctor about my blood pressure?

You should discuss your blood pressure with your doctor at your regular check-ups. If you get a reading in the "High Blood Pressure" (Stage 1 or 2) range, you should consult your doctor. If your reading falls into the "Hypertensive Crisis" category, seek emergency medical care immediately.

How can I get the most accurate reading at home?

To get an accurate reading:

  • Avoid caffeine, exercise, and smoking for at least 30 minutes before.
  • Rest quietly for 5 minutes with your back supported and feet flat on the floor.
  • Keep your arm supported on a flat surface, with the cuff at heart level.
  • Take 2-3 readings, one minute apart, and use the average.
What factors can affect my blood pressure reading?

Many factors can cause temporary changes in blood pressure, including stress ("white coat" hypertension at the doctor's office), physical activity, what you've eaten (salt, caffeine), medication, and even the time of day. This is why a diagnosis is based on multiple readings over time.

What if my systolic and diastolic numbers are in different categories?

Your blood pressure category is determined by the *higher* of the two numbers. For example, if your systolic is 118 (Normal) but your diastolic is 82 (Stage 1), your classification is High Blood Pressure (Stage 1).

Tool developed by Ugo Candido. Content verified by the CalcDomain Medical Review Board for clinical accuracy.

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