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Know Your Numbers

Blood pressure is typically recorded as two numbers, written as a ratio like this:

80   mm Hg


Read as "120 over 80 millimeters of mercury"



The top number, which is also the higher of the two numbers, measures the pressure in the arteries when the heart beats (when the heart muscle contracts).


The bottom number, which is also the lower of the two numbers, measures the pressure in the arteries between heartbeats (when the heart muscle is resting between beats and refilling with blood).

This chart reflects blood pressure categories defined by the American Heart Association.

Blood Pressure
mm Hg (upper #)
mm Hg (lower #)
Normal less than 120 and less than 80
Prehypertension 120139 or 8089
High Blood Pressure
(Hypertension) Stage 1
140159 or 9099
High Blood Pressure
(Hypertension) Stage 2
160 or higher or 100 or higher
Hypertensive Crisis
(Emergency care needed)
Higher than 180 or Higher than 110


How do you check your blood pressure? 


How is high blood pressure diagnosed?

The American Heart Association recommends a blood pressure screening at your regular healthcare visit or once every 2 years, if your blood pressure is less than 120/80 mm Hg. Your blood pressure rises with each heartbeat and falls when your heart relaxes between beats. While BP can change from exercise, stress or sleep, it should normally be less than 120/80 mm Hg (less than 120 systolic AND less than 80 diastolic) for an adult age 20 or over.

A single high reading does not necessarily mean that you have high blood pressure. However, if readings stay in the Stage 1 Hypertension phase of 140/90 mm Hg or above, your doctor will likely recommend a treatment program of lifestyle changes and often prescription medication.

If, while monitoring your blood pressure, you get systolic readings in the Hypertensive Crisis of 180 mm Hg or higher OR a diastolic reading of 110 mm HG or higher, seek immediate medical treatment.

To learn more about blood pressure numbers and what they mean for your health, visit the American Heart Association's High Blood Pressure Health Risk Calculator.