Bar to pounds per square inch (bar to psi)

One bar is exactly 100,000 pascals and one psi is exactly 4.4482216152605 divided by 0.00064516 pascals, so the factor 14.503773773 is derived from two definitions and is exact in principle.

Worked through: 2.2 bar x 14.5037738 = 31.9083 psi.

Going the other way, one pound per square inch is 0.0689475729 bar.

For mental arithmetic: Multiply by 14.5.

Tires, mostly. The European placard reads in bar and the American gauge in psi, and the rule of thumb is that one bar is about 14.5 psi, so a 2.2 bar front tire is 32 psi. The thing that catches people is gauge versus absolute: a tire gauge reads pressure above atmospheric, so a tire at '32 psi' is at about 46.7 psi absolute. Weather and vacuum work in absolute, tires and hydraulics in gauge, and the two differ by one atmosphere, which is 14.7 psi.

Precision is worth matching to the input. A measurement given as 1 bar carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.