Pressure Converter

How to use Pressure Converter

1. Enter the pressure reading.
2. Pick the unit it was measured in.
3. Read the equivalent in every other unit — updates live as you type.
4. One standard atmosphere is exactly 101,325 Pa, which is 1.01325 bar or 14.6959 PSI.
5. Millibar and hectopascal are identical in size — a weather chart reading of 1013 mbar is 1013 hPa.
6. Tyre and gauge readings are pressure above atmospheric; add one atmosphere to get absolute pressure.

The pascal is small, which is why nobody quotes it

One pascal is one newton per square metre — roughly the pressure a sheet of paper exerts lying flat. Atmospheric pressure is about 101,325 of them, so real-world figures in pascals are unwieldy and everyone reaches for a multiple instead: kilopascals for tyres and gas, bar for hydraulics and diving, hectopascals or millibars for weather (they are the same size, which is why a forecast reading of 1013 works in either), and megapascals for material strength.

Gauge pressure and absolute pressure are different numbers

A tyre gauge reading 32 PSI means 32 PSI above the surrounding air, not 32 PSI in total — the absolute pressure is about 46.7 PSI. That is gauge pressure, written PSIG; absolute is PSIA. A flat tyre reads zero on a gauge and still contains air at one atmosphere. This converter works on whatever number you type, so the conversion is correct either way, but adding 14.7 PSI (or 101.3 kPa) at the wrong moment is how gauge and absolute figures get mixed up in a calculation.

Where each unit still lives

PSI: tyres, compressed air and plumbing in the United States. kPa: tyres and gas pressure almost everywhere else, and tyre placards in many cars show both. bar: hydraulics, espresso machines (nine bar at the group head), scuba cylinders (200 or 300 bar). Millibar and hectopascal: meteorology. Inches of mercury: American aviation altimeters and older barometers. Torr, which is a millimetre of mercury: vacuum work and blood pressure, where 120/80 means millimetres of mercury. Inches of water: very low pressures such as ventilation ducts and gas appliance regulators.