Convert between torr (mmHg) and atmospheres (atm), plus other common pressure units like pascals, PSI, and bar.
Last updated: March 2026 | By Patchworkr Team
Torr is a unit of pressure named after Evangelista Torricelli, inventor of the barometer. One torr is approximately equal to one millimeter of mercury (mmHg). It's commonly used in vacuum measurements and medicine (blood pressure).
Atmosphere (atm) is a unit of pressure defined as exactly 101,325 pascals. It represents the average atmospheric pressure at sea level. The relationship is simple: 1 atm = 760 torr exactly.
These units are essential in chemistry, physics, medicine, and engineering for measuring and comparing pressures in various systems from vacuum chambers to blood pressure monitors.
Yes, for practical purposes. 1 torr is defined as exactly 1/760 of an atmosphere, while 1 mmHg is the pressure of 1mm of mercury. They differ by less than 0.000015%, so they’re used interchangeably.
Standard atmospheric pressure at sea level supports a column of mercury 760mm high in a barometer. This became the definition: 1 atmosphere = 760 torr = 760 mmHg.
Use torr for vacuum systems, low pressures, and blood pressure measurements. Use atm for standard atmospheric conditions and chemistry calculations. Both are common in scientific literature.
Pascal (Pa) is the SI unit of pressure. 1 torr = 133.322 Pa. Pascals are preferred in modern scientific work, but torr remains common in vacuum technology and medicine.
Blood pressure is measured in mmHg (millimeters of mercury), which is essentially the same as torr. Normal blood pressure is around 120/80 mmHg, meaning 120 torr systolic and 80 torr diastolic.
Rough vacuum: 760 to 1 torr. Medium vacuum: 1 to 10⁻³ torr. High vacuum: 10⁻³ to 10⁻⁹ torr. Ultra-high vacuum: below 10⁻⁹ torr. Space has about 10⁻¹⁴ torr.
Related Tools
Convert between force units.
Convert torque from inch-pounds to newton-meters.
Convert torque between inch-pounds and foot-pounds.
Convert pounds-force to newtons.
Convert torque from newton-meters to foot-pounds.
Convert torque from newton-meters to inch-pounds.