The torr is a unit of pressure. Its symbol is Torr. One torr was originally defined as the pressure exerted by a depth of one millimeter of mercury (mmHg), and then as 1/760 of a standard atmosphere.

Because the standard atmosphere is now a defined quantity in the SI system of units, the torr is hence defined as exactly 101325 / 760 = 2533.125 / 19 ≈ 133.3223684 pascals. Although the torr is still in common use in low-pressure engineering, the pascal is now the recommended unit of pressure.

This unit (usually under the millimeter of mercury name) remains the most common unit for the measurement of blood pressure in much of the world.

The torr unit is named after Evangelista Torricelli.

See also

• Manometric pressure unit

External links

• Conversion of all pressure units (http://www.sengpielaudio.com/calculator-pressure.htm)
• NPL - pressure units (http://www.npl.co.uk/pressure/punits.html)

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