Kilopascals to PSI

The kilopascal is the SI way to state tire pressure, and placards in Canada, Australia, New Zealand, Japan and many other markets list kPa first, often with psi or bar beside it. Typical values: 200 kPa is 29.0 psi, 220 kPa is 31.9 psi, 230 kPa is 33.4 psi, 240 kPa is 34.8 psi and 250 kPa is 36.3 psi.

If your gauge only reads psi, convert the placard figure once and write it down for the glove box. Bar is the other metric option, and 100 kPa is exactly 1 bar, so 230 kPa and 2.3 bar are the same setting; the psi to bar page covers that side.

Standard sea-level pressure is 101.325 kPa, which is 14.696 psi or 1 atm. Weather services in many countries give the same value as 1,013.25 hPa, since a hectopascal is a tenth of a kilopascal. Pressure falls with altitude: at about 1,600 m, the height of Denver, typical air pressure is around 83 kPa, roughly 12 psi, which is why packaged snacks puff up on mountain drives.

Gauge readings ignore this background pressure. A tire gauge reading 230 kPa at sea level means the air inside is about 331 kPa absolute.

Material strengths and hydraulic ratings use megapascals, a thousand kPa. One MPa is 145.04 psi, so concrete specified at 30 MPa is about 4,350 psi and a 20 MPa hydraulic line is about 2,900 psi. Divide kPa by 7 for a quick estimate that comes out 1.5% low. The unit converter lists pascals, bar and atmospheres as well.