A chart detailing blood pressure ranges is located on the National Heart, Blood and Lung Institute website. Blood pressure is expressed as a ratio. The top number measures systolic pressure. The bottom number measures diastolic pressure. Together, they reflect the pressure in the arteries as the heart beats and rests.
Normal blood pressure for adults is a reading of less than 120/80 mmHg. Prehypertension is indicated by a systolic reading between 120 and 139 mmHg or a diastolic reading between 80 and 89 mmHg, according to the National Heart, Blood and Lung Institute. High blood pressure is divided into two stages. Stage 1 is a systolic reading between 140 and 159 mmHg or a diastolic reading between 90 and 99 mmHg. Stage 2 is anything above 160/100 mmHg. As blood pressure rises, so does the risk for cardiovascular health problems.