To convert kPa to psi, multiply by 0.14504. 1 kPa equals 0.14504 psi, about 1% of the atmosphere at sea level.
| kPa | psi |
|---|---|
| 1 kPa | 0.14504 psi |
| 2 kPa | 0.29008 psi |
| 5 kPa | 0.72519 psi |
| 10 kPa | 1.4503774 psi |
| 25 kPa | 3.6259434 psi |
| 50 kPa | 7.2518869 psi |
| 100 kPa | 14.503774 psi |
| 250 kPa | 36.259434 psi |
| 500 kPa | 72.518869 psi |
| 1000 kPa | 145.03774 psi |
Definition: 1,000 pascals - a pascal itself being the pressure from one newton of force spread over one square meter.
History: Named after Blaise Pascal, the French mathematician and philosopher who directed one of history's most famous pressure experiments in 1648: he had his brother-in-law carry a mercury barometer up the Puy de Dôme mountain in central France, proving that atmospheric pressure drops with altitude and settling a fierce scientific debate about whether a true vacuum could exist. Despite the honor, the unit itself wasn't officially named "pascal" until 1971, over 300 years after his death - before that, scientists just wrote "newtons per square meter."
Current use: Weather reports (as kilopascals or the closely related hectopascal), bicycle tire pressure labels, and most engineering specs outside the US.
Definition: The pressure created by one pound of force pushing on one square inch of area.
History: PSI grew out of the imperial engineering tradition - especially the steam engine era, when engineers needed a practical way to describe boiler pressure using units they already had (pounds and inches) rather than inventing something new.
Current use: Car and bike tire pressure gauges in the US, home plumbing and HVAC systems, and scuba tank ratings are all commonly quoted in PSI.
The factor is 0.145038, which is derived rather than defined, so any decimal you see has been rounded somewhere.
No simple round multiplier is close enough to be useful, so this is one to look up rather than estimate. The exact factor is 0.145038.
Going the other way, one psi is 6.895 kPa, which is usually the easier direction to work in. Because the forward factor is small, watch the decimal place rather than the digits: a factor-of-ten slip is the common error, not a rounding one.
To anchor the scale: 10 kPa is about 1.45 psi.