Difference Between Systolic Blood Pressure and Diastolic Blood Pressure


Main Difference

During cardiac cycle, minimum pressure of blood in arteries when ventricles are filled with blood is called diastolic blood pressure. In diastolic stage, heart relaxes and rearranges itself. At the end of cardiac cycle, extreme pressure during the contraction of ventricles is called systolic blood pressure. In systolic stage, heart pushes blood into arteries.

Comparison Chart

Systolic Blood PressureDiastolic Blood Pressure
DefinitionThe force of blood on the walls of arteries during the heart beating is called systolic blood pressure.The force of blood on the walls of arteries between the time intervals of heart beating is called diastolic blood pressure.
Rangenormally 120 or belownormally 80 or below
Ideal Blood Pressure120-139Near 80
HypertensionAbove 140Above 80
Measuring Unitmillimeters of mercury (mmHg)millimeters of mercury (mmHg)
Measuring equipmentSphygmomanometerSphygmomanometer

What is Systolic Blood Pressure?

Heart continuously pumps blood into arteries, so blood pressure varies (rise and fall) during each heart beating. Physicians measures blood pressure in two digits first is higher than second. Normal blood pressure of a person is written as 120/80 mmHg. Top or first number of this expression is called systolic blood pressure. If systolic blood pressure is going to be rise above 120 mmHg, then person will be at risk of hypertension which is also known as hypertension. Systolic blood pressure at range 120-139 is called pre-hypertension, and if systolic blood pressure increases more above 140 mmHg, the patient will be hypertensive. Systolic blood pressure increases in older people more as compared to young because of hardening of arteries and no compliance of aorta with age. Systolic hypertension increases load on ventricles and causes heart failure, left ventricular hypertrophy and coronary ischemia. If systolic blood pressure is going to be lower than 120 mmHg, then person will be at the risk of hypotension (lower blood pressure). Word “systolic” has derived from Greek language which “drawing or contraction at the same time”. Normal range of systolic blood pressure measurement in children is 95 to 100 mmHg while for adults it ranges 90 to 120 mmHg.


What is Diastolic Blood Pressure?

Bottom number of blood pressure expression (120/80 mmHg) is called diastolic blood pressure. Diastolic blood pressure is always lower than systolic blood pressure because this force is exerting when heart is in relaxing state after pumping blood into arteries. During this time, heart refills itself with new blood and gets oxygen from lungs. The person will be at risk of high blood pressure if diastolic blood pressure will be in the range of 80-89 mmHg which is also called pre-hypertension. If diastolic blood pressure measures above 90 mmHg then patient will be hypertensive. Isolated diastolic hypertension (IDH) is more common in adults. In most cases, cause of diastolic hypertension remains unknown which is also referred as essential or primary hypertension. But some studies assume that elevation of angiotensin in vessels, inappropriate contaction of small muscles in arteries and genetic factors can be possible reasons. Diastolic hypertension eventually becomes a cause of systolic hypertension, kidney disease, sleep apnea and thyroid problem. If diastolic blood pressure reading measures lower than 80 mmHg then person may be at the risk of hypotension. Word “diastolic” has derived from Greek language which means “drawing apart”. Diastolic measurement in children is about 65 mmHg while it ranges 60 to 80 mmHg for adults.

Systolic Blood Pressure VS. Diastolic Blood Pressure

  • Both systolic and diastolic blood pressures are types of blood pressure.
  • Both types of blood pressures are measured at the same time with same procedure using the same equipment (Sphygmomanometer).
  • Variation in blood pressure causes changes in both types of blood pressure.
  • Variation in both types of blood pressure has significance in heart diseases especially difference in both at the same time.
  • Systolic blood pressure occurs during the contraction of ventricles during heart beating.
  • Diastolic blood pressure occurs in the start of cardiac cycle between heart beating.
  • Systolic blood pressure is the pressure of blood on arteries and vessels.
  • Diastolic blood pressure is the pressure of blood only on arteries.
  • During systolic stage, only left ventricle contacts and blood vessels remain in contracted state.
  • During diastolic stage, both ventricles of heart fill with blood while blood vessels remain in relaxed state.
  • Systolic blood pressure measuring is important in older age for diagnosis of disease.
  • Diastolic blood pressure measuring is important in adult age for diagnosis of any disease.
Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

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