Torr to Atm Converter

The torr was redefined in 1954 to be exactly one 760th of a standard atmosphere, with no further reference to mercury. The standard atmosphere itself is also exact by international convention: 1 atm = 101,325 pascals. That gives 1 torr = 101325 / 760 = 133.32236842 Pa exactly. The 760 figure traces back to Evangelista Torricelli's 1644 barometer experiment, where atmospheric pressure at sea level supported a mercury column 760 mm tall, but modern definitions cut the dependence on mercury so the unit no longer drifts with temperature or local gravity.

No, though they are extremely close. 1 torr is exactly 101,325 / 760 Pa, or about 133.322368421 Pa. A conventional mmHg is 133.322387415 Pa. The relative difference is about 0.000014%, and 760 conventional mmHg exceeds 760 torr by about 0.0144 Pa. This converter preserves the distinct factors.

Depends on the subfield. Bench chemists in the US still write gas-law problems in atm and torr because most general-chemistry textbooks do. Physical chemists and SI-pure publications use pascals or kilopascals (1 atm = 101.325 kPa). Vacuum specialists use torr (high vacuum) and millitorr or microtorr (ultra-high vacuum), because a typical high-vacuum chamber sits at 1e-6 torr (about 1.3e-4 Pa). Industrial chemists and engineers use bar (1 bar = 100 kPa, very close to 1 atm). Medical and meteorological work uses mmHg (blood pressure, mercury barometers). Process engineering in the US uses psi (pounds per square inch). This converter covers all seven so you can move between them without re-deriving the factor.

Evangelista Torricelli was an Italian physicist and mathematician, Galileo's last assistant, who in 1644 invented the mercury barometer to settle a long-running dispute about whether vacuums could exist (Aristotle said no). He filled a one-meter glass tube with mercury, inverted it into a basin, and watched the column drop to 760 mm. The space above was the first sustained laboratory vacuum, and the column height let him measure atmospheric pressure for the first time. He named neither the unit nor the device after himself: Marin Mersenne renamed the apparatus a barometer, and the torr was named in his honor only in 1913 by the International Committee on Weights and Measures, almost 270 years after his death.

Standard atmospheric pressure at sea level is 1 atm = 760 torr = 101.325 kPa = 1.01325 bar = 14.6959 psi. A car tire is typically 32 to 35 psi (about 2.2 to 2.4 atm, 220 to 240 kPa). Normal blood pressure is around 120 over 80 mmHg (around 0.158 atm systolic). A standard SCUBA tank holds 3000 psi (about 204 atm, 207 bar). Earth's atmosphere at Mount Everest's summit is around 253 torr (0.33 atm). A laboratory rough vacuum runs at 1 torr (1.3e-3 atm), high vacuum at 1e-6 torr, and ultra-high vacuum below 1e-9 torr. A standard mercury barometer column at sea level reads 760 mm, which is exactly where the unit comes from.