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Pressure Converter

Convert pressure between psi, bar, millibar, pascal, kPa, MPa, atmosphere, torr, mmHg, inHg, ksi and kgf/cm², using exact standard definitions.

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Convert a pressure

How to use the converter

Type a pressure in the Value box, choose the unit you have and the unit you want, then press Convert. The swap button flips the two units, and a table below the result shows the same pressure in all twelve units.

The converter starts on psi to bar, the pair most people need for tyre pressures. Negative values are accepted, because gauge readings below atmospheric pressure (a vacuum) are negative.

Unit definitions

All conversions go through the pascal (Pa), the SI unit: one newton per square metre.

  • 1 kilopascal (kPa) = 1,000 Pa; 1 megapascal (MPa) = 1,000,000 Pa
  • 1 bar = 100,000 Pa exactly; 1 millibar (mbar) = 100 Pa, the same as a hectopascal (hPa)
  • 1 standard atmosphere (atm) = 101,325 Pa exactly
  • 1 torr = 101,325 / 760 Pa ≈ 133.322368 Pa
  • 1 millimetre of mercury (mmHg) = 133.322387415 Pa
  • 1 inch of mercury (inHg) = 25.4 mmHg ≈ 3,386.38864 Pa
  • 1 psi (pound-force per square inch) ≈ 6,894.757293168 Pa, from 1 lbf = 0.45359237 kg × 9.80665 m/s² and 1 in = 0.0254 m
  • 1 ksi = 1,000 psi
  • 1 kgf/cm² (technical atmosphere) = 98,066.5 Pa exactly

Torr and mmHg are often treated as the same, but they differ by about 0.14 parts per million: 1 atm is exactly 760 torr and about 759.999892 mmHg.

Tyre pressure examples

Car tyres are usually quoted in psi in the US and in bar or kPa elsewhere.

  • 32 psi = 32 × 6,894.757 / 100,000 ≈ 2.206 bar
  • 35 psi ≈ 241.3 kPa
  • 2.5 bar ≈ 36.26 psi

Tyre gauges show gauge pressure, the amount above the surrounding air. The absolute pressure inside the tyre is about 1 atm (14.7 psi) higher.

Weather examples

Standard sea-level pressure is 1013.25 mbar (hPa), which equals 1 atm. In inches of mercury that is 101,325 ÷ 3,386.38864 ≈ 29.92 inHg, the figure used in US weather reports and aviation. A reading of 30.00 inHg is about 1015.92 mbar, typical of fair weather, while a deep storm may drop below 980 mbar (about 28.94 inHg).

Good to know

  • Results are shown with up to six decimal places; very small values use scientific notation.
  • 1 bar is close to, but not the same as, 1 atm: 1 atm = 1.01325 bar.
  • Blood pressure is measured in mmHg, and vacuum gauges often use torr.

Frequently asked questions

How many bar is 32 psi?

32 psi is about 2.21 bar. One psi is 6,894.757 Pa and one bar is 100,000 Pa, so multiply psi by about 0.0689476 to get bar.

Is a bar the same as an atmosphere?

Almost, but not exactly. One bar is 100,000 Pa and one standard atmosphere is 101,325 Pa, so 1 atm = 1.01325 bar and 1 bar ≈ 0.986923 atm.

What is the difference between torr and mmHg?

One torr is defined as 1/760 of a standard atmosphere (about 133.322368 Pa). One millimetre of mercury is defined as 133.322387415 Pa. The difference is less than one part in a million, so for everyday use they are interchangeable.

Is a millibar the same as a hectopascal?

Yes. Both equal 100 pascals. Weather services often use hPa, while older charts and some countries use mbar; the numbers are identical, so 1013.25 hPa is 1013.25 mbar.