Blood pressure is the force of your blood pushing against the walls of your arteries. Each time your heart beats, it pumps out blood into the arteries. Your blood pressure is highest when your heart beats, pumping the blood. This is called systolic pressure. When your heart is at rest, between beats, your blood pressure falls. This is the diastolic pressure. 120/80 or lower is normal blood pressure. 140/90 or higher is high blood pressure. Between 120 and 139 for the top number, or between 80 and 89 for the bottom number is pre-hypertension.