A pressure converter changes a force-per-area reading from one unit into another — PSI to bar, kilopascals to atmospheres, or millibars to torr. It is needed for tyre inflation, weather readings, diving, industrial equipment and lab work, where the same quantity is quoted in whichever unit the local convention or the gauge happens to use. This tool covers Pa, kPa, MPa, bar, mbar, PSI, atm and torr.
The formula. Every value passes through one base unit, the pascal (one newton per square metre). The factors are 1 kPa = 1,000 Pa, 1 bar = 100,000 Pa, 1 mbar = 100 Pa, 1 PSI = 6,894.76 Pa, 1 atm = 101,325 Pa exactly, and 1 torr = 133.322 Pa (one millimetre of mercury). A value is multiplied to pascals, then divided by the target unit's factor: result = value × factor(from) ÷ factor(to).
Worked example. A car tyre inflated to 32 PSI is 32 × 6,894.76 = 220,632 Pa, which is 2.21 bar or 220.6 kPa — the three numbers you will see on a European, a British and an Indian gauge for the same tyre. Standard atmospheric pressure is 101,325 Pa = 1 atm = 1,013.25 mbar = 14.70 PSI, which is why sea-level weather charts hover around 1013 mbar.
Where it's used. Tyre placards are printed in PSI, bar or kPa depending on the market; weather forecasts use hectopascals or millibars (they are numerically identical); scuba and industrial gas cylinders are rated in bar or PSI; and vacuum work uses torr. One caution: gauges usually read gauge pressure, measured relative to the surrounding air, while absolute pressure adds the roughly 14.7 PSI the atmosphere is already applying.