What Is Blood Pressure?
Blood pressure is the force of blood pushing against the walls of arteries.
Blood pressure is measured with two numbers.
- The systolic blood pressure (the number on top) is the pressure caused when the heart contracts and pushes out blood
- The diastolic blood pressure (the number on the bottom) is the pressure when the heart relaxes and fills with blood between heartbeats
Blood pressure readings are reported as the systolic blood pressure number over the diastolic blood pressure number, such as 120/80 mmHg (“120 over 80”).
What Is Normal Blood Pressure by Age?
Blood pressure ranges for adults are:
- High: Systolic (top number) of 130 or above and/or diastolic (bottom number) of 80 or above
- Elevated: Systolic (top number) between 120 and 129 and diastolic (bottom number) of 79 or below
- Normal: Systolic (top number) of 119 or below and diastolic (bottom number) of 79 or below
- Low: Systolic (top number) of less than 100 and/or diastolic (bottom number) of less than 60
The normal blood pressure for adolescents 13 years or older is less than 120/80 mmHg.
In younger children, the normal range for blood pressure is determined by the child's sex, age, and height. The normal range is expressed as a percentile, similar to charts used to track children's growth.
Blood pressure is separated into three categories based upon the child's blood pressure percentile:
- High blood pressure (hypertension): Either systolic and/or diastolic blood pressure 95th percentile or greater measured on three or more separate occasions, or if blood pressure exceeds 130/80 mmHg.
- Elevated blood pressure: Systolic and/or diastolic blood pressure is in the 90th percentile or greater, but less than the 95th percentile or if blood pressure exceeds 120/80 mmHg (even if less than the 90th percentile for age, gender, and height).
- Normal blood pressure: Both systolic and diastolic blood pressure are less than 120/80 mmHg in adolescents 13 years or older, and for younger children blood pressure that is less than the 90th percentile based on the child’s sex, age and height
- Low: There is no specific range for pediatric low blood pressure because of the variability of sizes and ages of children