How this calculator works
The pascal is the SI derived unit of pressure: one newton per square metre. Every conversion on this page passes through the pascal, so the chosen input unit is first expressed in pascals and then divided by the number of pascals in the target unit. The standard atmosphere is exactly 101,325 Pa, the bar is exactly 100,000 Pa, and the torr is exactly 1/760 of an atmosphere. The pound per square inch uses the international pound-force and square inch. The millimetre and inch of mercury use the conventional values from NIST rather than the height of a real mercury column, which changes with temperature and local gravity.
Formula
Target unit = pascals / pascals per target unit. 1 kPa = 1,000 Pa; 1 MPa = 1,000,000 Pa; 1 bar = 100,000 Pa; 1 psi = 6,894.757293168 Pa; 1 atm = 101,325 Pa; 1 torr = 101,325 / 760 Pa = 133.322368421 Pa; 1 mmHg = 133.322387415 Pa; 1 inHg = 3,386.389 Pa.
Worked example
A standard atmosphere of 101,325 Pa is 101.325 kPa, 0.101325 MPa, 1.01325 bar, 14.6959487755 psi, 1 atm, 760 torr and about 759.9999 mmHg. A pressure of 6,894.757293168 Pa is exactly 1 psi.
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Frequently asked questions
What is one pascal?
One pascal is one newton of force spread over one square metre. It is a small unit, so practical pressures are often written in kilopascals, megapascals or bar.
Is the torr the same as a millimetre of mercury?
Not exactly. The torr is defined as 1/760 of a standard atmosphere, while the conventional millimetre of mercury is 133.322387415 Pa in this engine. The difference is less than one part in a million.
Is bar an SI unit?
No. The bar is accepted for use with the SI but is not an SI unit. One bar is exactly 100,000 Pa, which is close to one atmosphere and convenient in industry.
Does this page convert gauge pressure to absolute pressure?
No. It changes the unit only. Gauge pressure is measured from the surrounding atmosphere and absolute pressure from a vacuum, so adding or subtracting one atmosphere is a separate step.