According to WebMD, a normal blood pressure is lower than 120/80. This means that the systolic number is 120 or lower, and the diastolic number is 80 or lower. The systolic number measures artery pressure when the heart contracts. The diastolic number measures artery pressure between heartbeats.
According to WebMD, any systolic blood pressure between 120 and 139 is considered to be prehypertensive. A diastolic number between 80 and 89 also indicates prehypertension. Hypertension, or high blood pressure, is indicated when the systolic number is greater than 140, and the diastolic number is greater than 90. Patients with blood pressure problems typically reduce it through lifestyle changes and medication.