How this calculator works
The standard atmosphere is defined as exactly 101,325 Pa, and one torr is exactly 1/760 of that atmosphere. The relationship is therefore exact, not a measured approximation. The millimetre of mercury readout uses the conventional 133.322387415 Pa value, so it differs from the torr by a tiny fraction.
Formula
atm = torr / 760. torr = atm x 760. pascals = torr x 101,325 / 760. psi = pascals / 6,894.757293168.
Worked example
760 Torr = 1 atm = 101,325 Pa = 101.325 kPa = 14.6959 psi. A vacuum of 10 Torr is 0.0131579 atm, or about 1,333.22 Pa.
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Frequently asked questions
Why are there exactly 760 torr in an atmosphere?
The torr was defined as 1/760 of a standard atmosphere so that the older millimetre-of-mercury scale would have a simple conversion. The definition is exact by construction.
Is torr used for vacuum measurements?
Yes. Vacuum systems often use torr or millitorr because the numbers are convenient between atmospheric pressure and high vacuum. One millitorr is 0.001 Torr.
Does temperature affect the conversion?
The torr and atmosphere conversion is defined and does not depend on temperature. The conventional millimetre of mercury is also a fixed definition here, although a real mercury column changes with temperature and local gravity.