Pressure converter
Convert between any two of 7 pressure units. Conversion runs in your browser.
More detailsUnits covered · Everyday pressure conversions · The unit depends on the industry · Millimetres of mercury · Gauge and absolute
Units covered
| Unit | Symbol | In pascals |
|---|---|---|
| Pascal | Pa | 1 |
| Kilopascal | kPa | 1,000 |
| Bar | bar | 100,000 |
| Pound per square inch | psi | 6,894.757 |
| Atmosphere | atm | 101,325 |
| Millimeter of mercury | mmHg | 133.322387 |
| Inch of mercury | inHg | 3,386.389 |
Everyday pressure conversions
| 1 of these | kPa | bar | psi | atm |
|---|---|---|---|---|
| Kilopascal | 1 | 0.01 | 0.1450377 | 0.009869233 |
| Bar | 100 | 1 | 14.503774 | 0.9869233 |
| Pound per square inch | 6.894757 | 0.06894757 | 1 | 0.06804596 |
| Atmosphere | 101.325 | 1.01325 | 14.695949 | 1 |
Each row is one of that unit, given in each of the others.
The unit depends on the industry
Pressure has more units in active use than almost any other quantity, because several fields standardised independently. The SI unit is the pascal, one newton per square metre, which is so small that meteorology works in hectopascals and engineering in kilopascals. A bar is 100,000 Pa, chosen to be roughly one atmosphere, and it survives in European engineering. psi dominates in the US, including tyre pressures everywhere they are sold.
Millimetres of mercury
Blood pressure is still quoted in millimetres of mercury, and so is vacuum work. The unit is literally the height of a mercury column that the pressure will support, which is why the original barometers were about 760 mm tall — one atmosphere. Aviation uses inches of mercury for altimeter settings in the US and hectopascals almost everywhere else, which is a genuine source of confusion in the cockpit.
Gauge and absolute
A tyre gauge reading zero does not mean the tyre is a vacuum; it means the pressure inside matches the atmosphere outside. Readings that measure against the surrounding air are gauge pressure, often written psig, and readings that measure against a vacuum are absolute, psia. They differ by one atmosphere, about 14.7 psi. The conversions here are between units and leave that reference point alone.