Pressure Converter

The page starts on psi to bar, since that is the pairing most drivers need first.

1. Enter the reading in Value. A decimal such as 2.4 or 29.92 is fine.
2. Select the unit printed on your gauge, label or report in From. Pay attention to the symbol: kPa is a thousand pascals, MPa a million, and mbar a thousandth of a bar.
3. Select the unit you need in To. The converted figure appears at once, with a relationship line such as 1 psi = 6.8948 kPa.
4. Press Swap units to reverse the conversion and confirm it round-trips.
5. Check the In every unit list to read the same pressure in all nine units at once, which saves repeated conversions when a manual quotes a different unit from your gauge.

Pressure has more everyday units than almost any other quantity, and each has settled in a particular field. The pascal itself is the SI unit, one newton per square metre, which is tiny, so practical work uses multiples.

The anchor values to remember are 1 atm = 101.325 kPa = 14.696 psi = 1,013.25 mbar, and 1 bar = 100 kPa = 14.504 psi. Standard atmospheric pressure is exactly 760 mmHg, and the tool uses the factor 101,325 / 760 pascals per mmHg so the two figures agree.

Take a tyre label printed in psi when your pump reads bar. 32 psi is 220.63 kPa, or 2.206 bar, and 35 psi is 2.413 bar. For a weather report, a barometer reading of 29.92 inHg is about 1,013.2 mbar, and 30 inHg is 101.59 kPa. A blood pressure of 120/80 mmHg is 16.0 and 10.7 kPa, the form used in some countries.

Always take the figure to use from the vehicle placard, usually found on the door pillar or in the handbook, not from a converter, and not from the maximum moulded on the tyre wall. The tool translates numbers; it does not know your load, tyre size or conditions. Readings of blood pressure belong with a health professional, not with a unit calculator.

Two technical limits apply. First, the tool does not distinguish gauge pressure, which is measured above the surrounding air as on a tyre gauge, from absolute pressure, which includes the atmosphere. Converting units does not add or remove that 1 atm, so keep track of which one your source means. Second, only the unit changes, not the physical situation, so a temperature effect on a sealed tank needs separate thought. The temperature converter, speed converter and energy converter cover neighbouring quantities, and the weight converter handles load ratings.

The same conversions turn up well beyond tyres. A diving or breathing-gas cylinder filled to 200 bar holds 2,900.75 psi, while one marked 3,000 psi is 206.84 bar. A household water supply of 3 bar is 43.5 psi. A pressure washer rated at 150 bar is 2,175.6 psi, and an industrial hydraulic line at 20 MPa is 200 bar.

For safety-critical equipment, read the rated working pressure on the cylinder, regulator or appliance itself and follow the maker and your training. Treat this tool as a way to compare numbers in different units, never as a source of limits.

Weather watchers may also like a sense of scale. Air pressure falls by very roughly 1 hPa for every 8 metres of climb near sea level, which is why the same barometer reads lower in the hills. Forecast charts quote pressure reduced to sea level so that stations at different heights can be compared.