Systolic pressure is the pressure of blood against the artery walls when the heart has just finished contracting or pumping out blood. (Diastolic pressure is the pressure of blood against the artery walls between heartbeats, when the heart is relaxed and filling with blood.)

Systolic blood pressure is the upper number of a blood pressure reading. For example, if a person’s systolic pressure is 120 millimeters of mercury (mm Hg) and the diastolic pressure is 80 mm Hg, blood pressure is recorded as 120/80 and read as “120 over 80.”