Blood Pressure Calculator
Blood pressure is one of the most important indicators of cardiovascular health. It is recorded as two numbers: systolic pressure (the force when the heart beats) over diastolic pressure (the force when the heart rests). This calculator takes your systolic and diastolic readings in millimetres of mercury (mmHg) and classifies them according to the American Heart Association's 2017 guidelines into categories: Normal, Elevated, Hypertension Stage 1, Hypertension Stage 2, or Hypertensive Crisis. Understanding your category helps you and your doctor decide on lifestyle changes or treatment. A single reading is not a diagnosis, but repeated high readings are a signal to act. Regular monitoring at home can provide your doctor with valuable data beyond what is captured in a clinic visit.
Blood pressure classification (AHA 2017)
| Category | Systolic | Diastolic | |
|---|---|---|---|
| Normal | < 120 | and | < 80 |
| Elevated | 120-129 | and | < 80 |
| Stage 1 Hypertension | 130-139 | or | 80-89 |
| Stage 2 Hypertension | ≥ 140 | or | ≥ 90 |
| Hypertensive Crisis | > 180 | and/or | > 120 |
Pulse pressure formula
Pulse Pressure = Systolic - Diastolic
Normal pulse pressure is roughly 40 mmHg. A consistently high pulse pressure (above 60 mmHg) can indicate arterial stiffness. A low pulse pressure (below 25 mmHg) may suggest reduced cardiac output.
Blood pressure: frequently asked questions
What do the two blood pressure numbers mean?
The top number (systolic) measures pressure in your arteries when your heart beats. The bottom number (diastolic) measures pressure when your heart rests between beats. Both are measured in millimetres of mercury (mmHg).
What is considered normal blood pressure?
According to the American Heart Association, normal blood pressure is less than 120 mmHg systolic and less than 80 mmHg diastolic. Readings of 120-129 / less than 80 are elevated, and 130 or higher / 80 or higher indicate hypertension.
How often should I check my blood pressure?
Adults with normal blood pressure should check at least once every two years. Those with elevated or high readings should monitor more frequently as advised by their doctor. Home monitoring is recommended for many patients.
What is hypertensive crisis?
A hypertensive crisis is a severe increase in blood pressure (180/120 mmHg or higher) that can cause organ damage. It requires immediate medical attention. Symptoms may include severe headache, chest pain, or shortness of breath.
Can a single reading diagnose hypertension?
No. Hypertension is diagnosed based on the average of two or more readings taken on two or more occasions. A single high reading may be due to stress, caffeine, or activity. Always consult a healthcare provider for diagnosis.
Official sources
- American Heart Association: Understanding Blood Pressure Readings.
- National Heart, Lung, and Blood Institute: High Blood Pressure.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.