psi to kg/cm² Conversion Table

The Exact Factors

The psi to kg/cm² conversion rests on two definitions: one kilogram-force per square centimetre is 14.2233 psi, and one psi is 0.070307 kg/cm². Neither figure is a rounded engineering approximation; both follow from the definitions of the kilogram-force and the inch. A third factor completes the set for European work, since 1 kg/cm² is 0.980665 bar, which makes psi to bar a direct 0.0689476.

Because kg/cm² and bar differ by less than 2 %, the two are often treated as the same unit on the shop floor. That is harmless at 6 bar and careless at 250 bar, where the gap is nearly 5 kg/cm². Run the psi to kg/cm² conversion properly first and convert to bar afterwards if bar is what the paperwork asks for.

psig, psia and the Zero Point

American datasheets write psig for gauge and psia for absolute, and sometimes just psi with no suffix at all. The psi to kg/cm² conversion is indifferent to which one it is handed, but the reader is not: 100 psia is 85.3 psig, and at low pressures that difference is most of the reading.

Settle the zero point before converting rather than after. A psi to kg/cm² conversion applied to the wrong reference produces a number that looks entirely reasonable and is wrong by one atmosphere.

Pressure Class Is Not a Pressure

This is where the psi to kg/cm² conversion is most often misapplied. ANSI Class 150 does not mean 150 psi. A carbon steel Class 150 flange is rated 285 psi at 38 °C, 200 psi at 204 °C and about 110 psi at 371 °C: the class is a curve, not a single number.

Converting 150 psi into 10.5 kg/cm² and treating that as the working limit of a Class 150 valve is therefore wrong in both directions — too conservative when cold, dangerously optimistic when hot. Take the rating from the pressure-temperature table for the actual body material and temperature, and only then apply the psi to kg/cm² conversion to that figure.

PN and Class Do Not Interchange

DIN and EN equipment is marked PN, which is close to bar at ambient temperature: PN 16 is 16 bar, or 16.3 kg/cm². The customary pairings are PN 20 with Class 150, PN 50 with Class 300, PN 110 with Class 600, PN 150 with Class 900, PN 260 with Class 1500 and PN 420 with Class 2500, and a psi to kg/cm² conversion is what puts the two columns on the same scale.

These are equivalences of rating only. A PN 16 flange and a Class 150 flange have different bolt circles and different numbers of bolts, so they will not bolt together whatever the psi to kg/cm² conversion says about their ratings. Matching the pressure figure is not the same as matching the flange.

Test Pressures Come From the Same Table

Shell testing is normally 1.5 times the 38 °C rating, so a Class 150 body held at 285 psi is tested at about 428 psi, which the psi to kg/cm² conversion puts at 30.1 kg/cm². Seat tests are lower. Where a test certificate quotes a figure matching none of these, it is usually quoting the working pressure rather than the test pressure.

Rounding

Convert once, at the end. Rounding 14.2233 to 14.2 costs little on a single reading but compounds through a chain of calculations, and the full figure is short enough to carry. Where a drawing already states both units, treat the original as the master and use the psi to kg/cm² conversion only to check it, never to overwrite it.

Related Conversion Tables

Pressure is one axis of a valve order and size is the other. The inch to mm metric conversion table covers the dimensional side, and the ANSI Class to DIN PN conversion sets the two rating systems side by side. Together with the psi to kg/cm² conversion on this page they cover most of what has to be checked before an ANSI valve is fitted into a DIN line.