Atmosphere ( unit ) - wikipedia Atmosphere ( unit ) Atmosphere Unit of Pressure Symbol atm Unit conversions 1 atm in...... is equal to... SI units 101.325 kPa U.S. customary units 14.69595 psi The standard atmosphere ( symbol : atm ) is a unit of pressure defined as 101 325 Pa ( 1.013 25 bar ). It is sometimes used as a reference or standard pressure. Contents 1 History 2 Pressure units and equivalencies 3 Other applications 4 See also 5 References History It was originally defined as the pressure exerted by 760 mm of mercury at 0 ° C and standard gravity ( g = 7000980665000000000 ♠ 9.806 65 m / s ). It was used as a reference condition for physical and chemical properties, and was implicit in the definition of the Centigrade ( later Celsius ) scale of temperature by defining 100 ° C as being the boiling point of water at this pressure. In 1954, the 10th Conférence Générale des Poids et Mesures ( CGPM ) adopted standard atmosphere for general use and affirmed its definition of being precisely equal to 7006101325000000000 ♠ 1013250 dynes per square centimetre ( 7005101325000000000 ♠ 101 325 Pa ). This defined both temperature and pressure independent of the properties of particular substance. In addition ( the CGPM noted ) there had been some misapprehension that it `` led some physicists to believe that this definition of the standard atmosphere was valid only for accurate work in thermometry. '' In chemistry and in various industries, the reference pressure referred to in `` Standard Temperature and Pressure '' ( STP ) was commonly 1 atm ( 101.325 kPa ) but standards have since diverged ; in 1982, the International Union of Pure and Applied Chemistry ( IUPAC ) recommended that for the purposes of specifying the physical properties of substances, `` standard pressure '' should be precisely 100 kPa ( 1 bar ). Pressure units and equivalencies Pressure units Pascal Bar Technical atmosphere Standard atmosphere Torr Pounds per square inch ( Pa ) ( bar ) ( at ) ( atm ) ( Torr ) ( lbf / in ) 1 Pa ≡ 1 N / m 10 6995101970000000000 ♠ 1.0197 × 10 6994986919999999999 ♠ 9.8692 × 10 6997750060000000000 ♠ 7.5006 × 10 0.000 145 037 737 730 1 bar 10 ≡ 100 kPa ≡ 10 dyn / cm 7000101970000000000 ♠ 1.0197 6999986920000000000 ♠ 0.986 92 7002750060000000000 ♠ 750.06 14.503 773 773 022 1 at 7004980665000000000 ♠ 98 066. 5 6999980665000000000 ♠ 0.980 665 ≡ 1 kgf / cm 0.967 841 105 354 1 735.559 240 1 14.223 343 307 120 3 1 atm 7005101325000000000 ♠ 101 325 7000101325000000000 ♠ 1.013 25 7000103319999999999 ♠ 1.0332 760 14.695 948 775 514 2 1 Torr 133.322 368 421 0.001 333 224 0.001 359 51 1 / 760 ≈ 0.001 315 789 1 Torr ≈ 1 mmHg 0.019 336 775 1 lbf / in 6894.757 293 168 0.068 947 573 0.070 306 958 0.068 045 964 51.714 932 572 ≡ 1 lbf / in A pressure of 1 atm can also be stated as : ≡ 7000101325000000000 ♠ 1.013 25 bars ≡ 7005101325000000000 ♠ 101 325 pascals ( Pa ) or 7002101325000000000 ♠ 101.325 kilopascals ( kPa ) ≡ 7003101325000000000 ♠ 1013. 25 millibars ( mbar or mb ) ≡ 7002760000000000000 ♠ 760 torr ( Torr ) ≈ 7002760001000000000 ♠ 760.001 mmHg, 0 ° C, subject to revision as more precise measurements of mercury 's density become available ≈ 7001299213000000000 ♠ 29.9213 inHg, 0 ° C, subject to revision as more precise measurements of mercury 's density become available ≈ 7000103322745279988 ♠ 1.033 227 452 799 886 kgf / cm2 ≈ 7000103322745279988 ♠ 1.033 227 452 799 886 technical atmosphere ≈ 7003103322745279988 ♠ 1033. 227 452 799 886 cm H O, 4 ° C ≈ 7002406782461732238 ♠ 406.782 461 732 2385 in H O, 4 ° C ≈ 7001146959487755134 ♠ 14.695 948 775 5134 pounds - force per square inch ( psi ) ≈ 7003211621662367394 ♠ 2116. 216 623 673 94 pounds - force per square foot ( psf ) = 1 ata ( atmosphere absolute ). The ata unit is used in place of atm to indicate that the pressure shown is the total ambient pressure, compared to vacuum, of the system being calculated or measured. For example, for underwater pressures, a pressure of 3.1 ata would mean that the 1 atm of the air above water is included in this value and the pressure due to water would total 2.1 atm. Notes : Jump up ^ Torr and mm - Hg, 0 ° C are often taken to be identical. For most practical purposes ( to 5 significant digits ), they are interchangeable. ^ Jump up to : This is the customarily accepted value for cm -- H O, 4 ° C. It is precisely the product of 1 kg - force per square centimeter ( one technical atmosphere ) times 1.013 25 ( bar / atmosphere ) divided by 0.980 665 ( one gram - force ). It is not accepted practice to define the value for water column based on a true physical realization of water ( which would be 99.997 495 % of this value because the true maximum density of Vienna Standard Mean Ocean Water is 0.999 974 95 kg / l at 3.984 ° C ). Also, this `` physical realization '' would still ignore the 8.285 cm -- H O reduction that would actually occur in a true physical realization due to the vapor pressure over water at 3.984 ° C. ^ Jump up to : NIST value of 13.595 078 ( 5 ) g / ml assumed for the density of Hg at 0 ° C Other applications Scuba divers and others use the word atmosphere and `` atm '' in relation to pressures that are relative to mean atmospheric pressure at sea level ( 1.013 bar ). For example, a partial pressure of oxygen is calibrated typically using air at sea level, so is expressed in units of atm. The old European unit technical atmosphere ( at ) is equal to 1 kilogram - force per square centimetre ( kgf / cm ), 7004980665000000000 ♠ 98 066. 5 Pa. See also Standard conditions for temperature and pressure Atmospheric pressure International Standard Atmosphere References Jump up ^ Resnick, Robert ; Halliday, David ( 1960 ). Physics for Students of Science and Engineering Part 1. New York : Wiley. p. 364. ^ Jump up to : BIPM Definition of the standard atmosphere Jump up ^ IUPAC.org, Gold Book, Standard Pressure Jump up ^ Scuba Diving & Other Fun Activities, The Difference Between An ATM & An ATA Retrieved from `` https://en.wikipedia.org/w/index.php?title=Atmosphere_(unit)&oldid=851351642 '' Categories : Units of pressure Atmosphere Hidden categories : All articles with unsourced statements Articles with unsourced statements from July 2017 Talk Contents About Wikipedia Afrikaans Беларуская Беларуская ( тарашкевіца ) ‎ Български Bosanski Català Čeština Dansk Deutsch Eesti Ελληνικά Español Euskara فارسی Français Gàidhlig Galego 한국어 Հայերեն हिन्दी Hrvatski Bahasa Indonesia Íslenska Italiano עברית Қазақша Latviešu Lietuvių Magyar Македонски മലയാളം Nederlands 日本 語 Norsk Norsk nynorsk Occitan Piemontèis Polski Português Română Русский Simple English Slovenčina Slovenščina Suomi Svenska தமிழ் ไทย Türkçe Українська Tiếng Việt West - Vlams Winaray 粵語 中文 47 more Edit links This page was last edited on 21 July 2018, at 18 : 03 ( UTC ). 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Question: 1 bar is equal to how many atmospheric pressure
Answer: 0.98692