Normal Blood Pressure
Many people define normal blood pressure as an average reading of 120/80 or below. An average blood pressure can only be determined when multiple readings are taken over at least three days. Several things (such as lifestyle and family history) can affect a person's blood pressure range. Be mindful of this when comparing your reading to what's considered "normal blood pressure."
Blood pressure is the amount of force (pressure) that blood exerts on the walls of the blood vessels as it passes through them. Most healthcare providers agree that healthy blood pressure can fall anywhere within the normal blood pressure range. However, blood pressure can also be too high or too low -- both of which can cause problems.
To measure your blood pressure, a fabric cuff is wrapped around your arm and then slightly inflated. The blood pressure is measured by a gauge attached to the cuff. Your healthcare provider reads the numbers from the gauge as air is released from the cuff. The device that reads blood pressure is called a sphygmomanometer. Blood pressure can also be measured with a special machine.
The two numbers that measure your blood pressure are written like a fraction: one number on top and one on the bottom. Healthcare providers consider a normal blood pressure reading to be 120/80 or below. However, it can actually fall anywhere in a range from 90/60 to 120/80 -- it's not just one set number.
The number on top of the reading is called the systolic pressure. It measures the pressure inside your blood vessels at the moment your heart beats. The number on the bottom is your diastolic pressure. It measures the pressure in your blood vessels between heartbeats, when your heart is resting.