What do you think of the barometer below? Which number does the pointer point to when the car is inflated?

Black on the outer ring is pounds per square foot. The inner ring is red in kilograms per square centimeter, and what we usually say is 2.5 or 3.0 refers to the inner ring red number. Generally, the air pressure is 2.5, but 2. 1 is recommended for empty cars or bumpy roads, and 2.7 is recommended for full load.

The black outer ring is the British unit psi (pounds per square inch), the red inner ring is kg/cm 2 (kilograms per square centimeter), and the standard unit in the international system of units is n/m 2 (Newton per square meter), that is, Pa (Pascal).

A standard atmospheric pressure is about1.01*105pa, i.e.1Newton/cm2, i.e.1.03kg/cm2.

Roughly speaking, a standard atmospheric pressure is the black 1 position on your watch. More precisely, it should be at the position of 1.03 on your watch.