Measuring blood pressure is quick and painless. Usually, the procedure involves using either a sphygmomanometer or a blood pressure machine. Blood pressure is measured in millimeters of mercury (mmHg) and recorded as two numbers -- systolic pressure over diastolic pressure.For example, the doctor or nurse might say 130 over 80 as a blood pressure reading. This is written as 130/80.easuring blood pressure is quick and painless. Usually, the procedure involves using either a sphygmomanometer or a blood pressure machine. Blood pressure is measured in millimeters of mercury (mmHg) and recorded as two numbers -- systolic pressure over diastolic pressure.