Which one of the following is considered normal blood pressure in man?

Normal blood pressure in a healthy adult is typically considered to be 120/80 mm Hg [1][t6]. The unit 'mm Hg' stands for millimeters of mercury, which is the standard unit of measurement for blood pressure [t2][t3]. The first number (120) represents the systolic pressure, which is the force exerted against the arterial walls when the heart contracts [c1][t4]. The second number (80) represents the diastolic pressure, which is the pressure in the arteries when the heart relaxes between beats [c1][t2]. While modern electronic gauges are now common, the abbreviation mm Hg remains the universal standard [t3]. Other units like mm water, mm blood, or mm air are not used for measuring human blood pressure [c1][t6]. Maintaining blood pressure below 120/80 mm Hg is considered optimal for cardiovascular health [t1][t5].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Blood pressure > p. 93