How this calculator works
All units convert through the pascal. The standard atmosphere is exactly 101,325 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 of mercury here uses the conventional value of 133.322387415 Pa, which differs very slightly from the torr. Inches of mercury use the conventional 0 degrees Celsius value of 3,386.389 Pa.
Formula
pascals = value x F(unit), where F is the factor listed for the chosen unit. 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
1 bar is 100,000 Pa, 14.5038 psi and 0.986923 atm. 1 atm is 1,013.25 hPa, 14.6959 psi and 760 torr. 30 psi is 206,842.718795 Pa, or about 2.06843 bar.
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Frequently asked questions
Is a torr exactly the same as a millimetre of mercury?
Not quite. The torr is defined as 1/760 atm exactly, while the conventional millimetre of mercury is 133.322387415 Pa. The difference is about one part in ten million, far below normal measurement accuracy.
What is the difference between gauge and absolute pressure?
Absolute pressure is measured from a vacuum. Gauge pressure is measured from the surrounding atmosphere, so it can be negative. This converter does not add or subtract atmospheric pressure; convert the number in the same convention you measured.
Why is bar not an SI unit?
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 for industrial pressure.