The optimal blood pressure range for healthy adults is between 90 millimeters of mercury, or mmHg, to 120 millimeters of mercury for systolic pressure and 60 millimeters of mercury to 80 millimeters of mercury for diastolic pressure, according to WebMD.
There are two components to a blood pressure reading, the systolic pressure reading and diastolic pressure reading, states WebMD. Systolic pressure is the maximum force, measured in mm of mercury, with which blood pushes against the artery walls when the heart muscle constricts. Diastolic pressure is the minimum force of the blood pushing against the artery walls when the heart muscle relaxes.
Normal blood pressure is considered 120 for systolic pressure and 80 for diastolic pressure. Hypertension, a high blood pressure condition, starts at 140 for systolic pressure and 90 for diastolic pressure, explains WebMD. Hypotension, a low blood pressure condition, does not have as strict a cutoff as hypertension and is generally diagnosed when a person becomes symptomatic; however, adults become at risk for hypotension when their blood pressure drops to below 90 for systolic pressure and 60 for diastolic pressure. People who have a blood pressure between 121 to 139 for systolic pressure and 81 to 89 for diastolic pressure are considered at risk for hypertension.