Pressure converters
13 conversions between 7 pressure units. Every page includes a live converter, the formula and a full conversion table.
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 |
All pressure conversions
- Pascals to Bars
- Kilopascals to Bars
- Kilopascals to Pounds Per Square Inch
- Kilopascals to Atmospheres
- Bars to Kilopascals
- Bars to Pounds Per Square Inch
- Bars to Atmospheres
- Pounds Per Square Inch to Kilopascals
- Pounds Per Square Inch to Bars
- Pounds Per Square Inch to Atmospheres
- Atmospheres to Kilopascals
- Atmospheres to Bars
- Atmospheres to Pounds Per Square Inch
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.