Pressure converter
Convert bar, psi, pascal, atmospheres and mmHg — from tyre pressures to weather charts to blood pressure.
Common pressure conversions
Every pressure unit
| Unit | Symbol | In pascals |
|---|---|---|
| Pascals | Pa | 1 |
| Hectopascals | hPa | 100 |
| Kilopascals | kPa | 1,000 |
| Megapascals | MPa | 1,000,000 |
| Millibars | mbar | 100 |
| Bar | bar | 100,000 |
| Standard atmospheres | atm | 101,325 |
| Pounds per square inch | psi | 6,894.76 |
| Torr | Torr | 133.322368 |
| Millimetres of mercury | mmHg | 133.322387 |
| Inches of mercury | inHg | 3,386.39 |
Questions
What pressure should my tyres be?
Look at the sticker in the driver's door frame or the fuel flap, not the number moulded into the tyre — that one is the tyre's maximum, not the manufacturer's recommendation. Most cars sit somewhere around 32 to 35 psi, which is roughly 2.2 to 2.4 bar.
Is my tyre gauge measuring absolute or gauge pressure?
Gauge pressure — the amount above the surrounding air. A tyre reading 32 psi actually contains about 46.7 psi absolute, because atmospheric pressure of roughly 14.7 psi is already pressing on the other side of the gauge. Conversions on this page are between units, and leave that distinction alone.
Why do weather forecasts use hectopascals and millibars interchangeably?
Because they are the same size. One hectopascal is exactly one millibar, so the change from mbar to hPa was a relabelling rather than a conversion. Standard sea-level pressure is 1013.25 of either.
What is the difference between torr and mmHg?
Almost nothing, and the difference is deliberate. A torr is exactly one seven-hundred-and-sixtieth of a standard atmosphere; the conventional mmHg is defined as exactly 133.322387415 pascals. They diverge by about one part in seven million — invisible in medicine, occasionally not in vacuum work.