Blood pressure of a person is measured by sphygmomanometer. The instrument is comprising of an inflatable air bladder cuff. With the help of the stethescope, the blood pressure in the artery is measured. The sphygmomanometer is usually graduated in units of millimeters of mercury, abbreviated as mm Hg. The cuff is tighten around the upper arm and the pressure is increased to fill the cuff with air. This blocks the flow of blood. The pressure is slowly released and the systolic and the diastolic pressure is checked. The first pressure recorded is systolic (120 mm Hg) and then the diastolic pressure (180 mm Hg).