Summary of common Pressure Units Version.00, /5/003 Portland State Aerospace Society <http://www.psas.pdx.edu> There are too many pressure units in common use. This is not nearly all of them. For PSAS, try to stick with Pa, or if you must psi.
PressureUnits From Atmosphere To Atm Bars Lb in psi in of Hg 0 C in of H O torr mm of Hg of H O Lb ft kgf m Pa microns dynes.035 4.695949 9.96 406.78 760 033.7 6. 033.7 035 760 0 3.035 0 6 Bars 0.98693 4.50377 9.53 40.463 750.06 09.7 088.54 097. 0 5 750.06 0 3 0 6 Lb in psi in of Hg 0 C in of H O torr mm of Hg of H O 6.8046 6.89476.0360 7.6799 5.75 70.30696 44 703.07 6894.76 5.75 68947.6 0 0 0 3 3.3405 3.38639 0.4954 3.595 5.4 34.535 70.76 345.35 3386.39.54 33863.9 0 0 0 4.4583.49089 3.673 7.35559.8683.54 5.033 5.40 49.089.8683 490.89 0 3 0 3 0 0 0 3 760.333 0 3.93368 0 3.9370 0 0.5354.3595.7845 3.595 33.3 000 333. 9.6784 9.80665.433.8959 0.39370 0.735559.0486 0 98.0665 735.559 980.665 0 4 0 4 0 0 Lb ft 4.754 0 4 4.78803 0 4 6.944444 0 3.439 0 0.9 0.3593 0.48848 4.8848 47.8803 359.3 478.803 kgf m 9.6784 0 5 9.80665 0 5.433 0 3.8959 0 3 3.9370 0 7.35559 0 0. 0.0486 9.80665 73.5559 98.0665 Pa 9.8693 0 6 0 5.450377 0 4.953 0 4 4.0463 0 3 7.5006 0 3.097 0.08854 0.097 0 7.5006 0 microns.3579 0 6.333 0 6.93368 0 5 3.9370 0 5 5.354 0 4 0 3.3595 0 3.7845 0 3.3595 0 0.333.333 dynes 9.8693 0 7 0 6.450377 0 5.953 0 5 4.0463 0 4 7.5006 0 4.097 0 3.08854 0 3.097 0 0. 750.06 0 3 Pressure Units conversion table to five decimal places, ordered by size of unit: (exact conversions are outlined with a box) Selected exact relations Bar 0 5 Pa 0 6 dynes Atm 760torr 035Pa gee 980665m s pound 0.4535937kg torr 000microns inch.54
PressureUnits 3 Introduction Measurements of pressure quantify the mechanical force exerted per area of surface. Since force is mass times acceleration, and area has dimensions of length squared, the dimensions of pressure are force area mass acceleration length m L m t L t L Since a force can conveniently be measured by comparing it to the weight of a known mass, many common units of pressure involve the Earth gravity acceleration factor ( g ). Since ( g ) varies by on order one part in 000 depending on where and when on the Earth s surface the measurement is made, literal use of weight to measure pressure has a low precision. To make the units consistent, an internationally recognized value for ( g ) has been established, see below. Definitions The Pascal ( Pa ) is the SI unit of pressure. One Pascal is defined as one ewton per square meter. The dyne is the cgs unit of pressure. The dyne is the cgs unit of force, defined as one g / s The torr is designed to replace the mm of Hg. The torr is defined to be /760 of a standard atmosphere. A torr is not exactly equal to the international standard millimeter of mercury, but it is within a factor of /7000000 which is close enough. An Atmosphere ( Atm ), or international standard atmosphere, is defined as 035 Pa. The Bar is yet another international unit of pressure. Bar = 0 5 Pa. The justification for the Bar is that it is related to other SI units by a power of 0, yet one Bar is close to one Atmosphere. When quoted in millibars, air pressure is always close to 000. One pound mass ( lbm ) is defined to be exactly 0.4535937kg One standard gravity ( gee ) is defined as 9.80665 m/s^ One pound force ( lbf ) is the force acting on a pound mass that produces an acceleration of one gee. One inch is defined as exactly.54 Conversions derived (for the skeptical) preliminaries gee 9.80665 m s 00.54 m ft 3.7405 s ()
4 PressureUnits The temperature at which water is densest is 3.98 C, at this temperature water weighs very close to gram per cubic centimeter. In fact, this was the idea behind the original definition of the gram. So when pressure is measured in terms of of water, it can be assumed that the reference area is one square centimeter, and the unit force is that exerted by one cubic centimeter of water (therefore one gram) under the influence of a standard gravity. This force is gram force 9.80665 kg m gee kg 000 000 s For English units: 9.80665 0 3 lbf gee lbm 9.80665 m 0.4535937 kg 4.448 s () (3) psi psi lbf in 4.448 03 in.54 00 m 6894.76Pa (4) psi 6894.76Pa Pa 035 6.8046 0 Atm (5) psi 6894.76Pa 0 5 Pa 6.89476 0 Bar Bar psi 6.8046 0 torr Atm 760 5.75 torr Atm (6) (7) psi 5.75 torr 5.75 mm of Hg 0 C 5.4 mm.0360 in of Hg 0 C in of H O 3.98 C gee kg 000 00 m 98.0665 Pa (8) (9)
PressureUnits 5 of H O 3.98 C 98.0665 Pa 6894.76 Pa 0.0433 psi psi (0) psi 0.0433 psi 70.307 of H O 3.98 C of H O () 70.307 of H O.54 7.6799 in of H O 3.98 C () kgf kg gee 9.80665 (3) psi 6894.76Pa 6894.76 m 9.80665 kgf 703.07 kgf m (4) Atm Atm 035Pa 6894.9 psi 4.6959 psi Pa 6. lbs ft (5) Atm 760torr 760mm of Hg 0 C 5.4 mm 9.96 in of Hg 0 C in Atm 035 m gee 000 00 gram force m 033.3 gram force 033.3 of H O.54 406.78 in of H O 3.98 C (6) (7)
6 PressureUnits Pascal Pa m kg m s m 000 g 0dyne 00 s Pa Pa 035 9.8693 0 6 Atm Pa 9.8693 0 6 torr Atm 760 Atm 7.5006 03 torr Pa 7.5006 0 3 torr 7.5006 0 3 mm of Hg 0 C 5.4 mm.953 04 in of Hg 0 C (8) (9) (0) () Pa m 9.80665 0 3 00 gram force m.097 0 gram force.097 0 of H O 3.98 C ().097 0 of H O.54 4.0463 03 of H O 3.98 C (3) Pa m 4.448.54 lbf 00 m.45038 0 4 lbf in.45038 04 psi (4) Pa.45038 0 4 psi.08854 0 lbs ft (5) Pa m 9.80665 kgf 0.097 kgf m (6)
PressureUnits 7 Mercury Units torr 760 Atm Pa 035 33.3 Pa 9.80665 kgf kgf m (7) torr 33.3 Pa.45038 0 4 psi Pa.93368 0 psi torr mm of Hg 0 C 5.4 mm 3.9370 0 in of Hg 0 C.7845 lbs ft (8) (9) torr 33.3Pa 33.3 m 9.80665 0 3 00 gram force m.3595 gram force.3595 of H O 3.98 C (30) torr.3595 of H O.54 0.5354 in of H O 3.98 C (3) Water Units of H O 3.98 C gram force 9.80665 0 3 00 gram force m 98.0665 m Pa 035 9.6784 0 4 Atm (3)