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### Definition

Pressure is a measure up of the force versus a surface. Press is usually expressed as a pressure per unit area.

You are watching: A device used to measure atmospheric pressure

Here is a comfortable conversion calculator because that some common pressure terms. The interpretations of each term are in the following section.

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 Pressure counter Calculator(Enter number on the left side; answer appears on the ideal side) This many: pounds per square inchatmospherestorrbarmillibarpascalskilopascalsmegapascalsgigapascals Equals pounds per square inchatmospherestorrbarmillibarpascalskilopascalsmegapascalsgigapascals

Many of the items friend will uncover on an MSDS come in both English (U.S. Customary System) and also metric (International mechanism or SI or cgs) units. The metric system has been adopted by nearly every country except the united States. Even in the U.S., scientists and also technical human being use the metric system due to the fact that of its lull of use.

If you room unfamiliar v the terms provided in these definitions, watch our mass unit and also distance unit counter pages.

Pounds per square inch(psi, PSI, lb/in2, lb/sq in)Commonly supplied in the U.S., however not elsewhere. Regular atmospheric push is 14.7 psi, which means that a column of waiting one square inch in area increasing from the Earth"s setting to room weighs 14.7 pounds.
Atmosphere(atm)Normal atmospheric press is identified as 1 atmosphere. 1 atm = 14.6956 psi = 760 torr.
Torr(torr)Based ~ above the initial Torricelli barometer design, one atmosphere of push will force the tower of mercury (Hg) in a mercury barometer to a elevation of 760 millimeters. A pressure that reasons the Hg tower to rise 1 millimeter is called a torr (you may still see the hatchet 1 mm Hg used; this has been changed by the torr. "mm Hg" is commonly used for blood pressure measurements). 1 atm = 760 torr = 14.7 psi.
Bar(bar)The bar virtually identical come the setting unit. One bar = 750.062 torr = 0.9869 atm = 100,000 Pa.
Millibar(mb or mbar)There space 1,000 millibar in one bar. This unit is provided by meteorologists who discover it easier to describe atmospheric pressure without making use of decimals. One millibar = 0.001 bar = 0.750 torr = 100 Pa.
Pascal(Pa)1 pascal = a pressure of 1 Newton per square meter (1 Newton = the pressure required to accelerate 1 kilogram one meter per second per second = 1 kg.m/s2; this is actually rather logical because that physicists and engineers, honest). 1 pascal = 10 dyne/cm2 = 0.01 mbar. 1 atm = 101,325 Pascals = 760 mm Hg = 760 torr = 14.7 psi.Kilopascal(kPa)The prefix "kilo" method "1,000", therefore one kilopascal = 1,000 Pa. Therefore, 101.325 kPa = 1 atm = 760 torr and 100 kPa = 1 bar = 750 torr.
Megapascal(MPa)The prefix "mega" way "1,000,000", so one megapascal = 1,000 kPa = 1,000,000 Pa = 9.869 atm = 145 psi.
Gigapascal(GPa)The prefix "giga" method "1,000,000,000", so one gigapascal = 1,000 MPa = 1,000,000 kPa = 1,000,000,000 Pa = 9,870 atm = 10,000 bar. Pressures of numerous gigapascals can transform graphite to diamond or do hydrogen a metallic conductor! such high pressures are rarely encountered in everyday life.
Some worked Examples

CORRECT: transform 5 atm to psi: WRONG: convert 5 atm to psi: CORRECT: convert 4,000 pascal come torr:  Safety Emporium has gas cylinder signs, racks, carts, clamps, lockouts and much more to ensure her workers" safety.

### SDS Relevance

Be an extremely careful to keep in mind the units once reading numbers on a safety Data Sheet. If you ever before perform a calculation of any type of sort, always remember to write the units beside each number in her calculation and make sure that they cancel properly. If lock don"t, your calculation was incorrect!