Definition
A unit of pressure equal to 1/760th of a standard atmosphere, which is approximately the pressure exerted by a one-millimetre column of mercury at 0 °C. One torr equals about 133.3 pascals.
Plain English
A small unit used to measure pressure. One torr is roughly the pressure produced by a column of mercury one millimetre tall.
Context Anchor
Seen in technical discussions of pressure, vacuum, oxygen systems, and high-altitude effects on the body.
Derivation
Named after Evangelista Torricelli, the 17th-century Italian physicist who invented the mercury barometer. The unit honours his discovery that the atmosphere exerts a measurable pressure that supports a column of mercury.
Why Pilots Care
Pilots may see torr in technical references about low pressure, vacuum, or oxygen effects at altitude. Knowing it is a pressure unit prevents confusion when comparing pressure values.
Grounding Statement
As an aircraft climbs and outside air pressure drops, that lower pressure could be expressed in torr.
Intuition Check
Torr is a pressure unit, not a force, speed, or altitude. It tells how much pressure is present, not how high the aircraft is.
Example Sentence 1
Standard sea-level atmospheric pressure is 760 torr.
Example Sentence 2
Calibration data listed the reference pressure as 0.05 Torr for the high-altitude altimeter simulation.