Standard atmosphere is a pressure defined as 101,325 Pa and used as unit of pressure (symbol: atm). Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Standard atmosphere is a non-SI unit that is internationally recognized. The 10th Conférence Générale des Poids et Mesures (10th CGPM) adopted standard atmosphere for general use and affirmed its definition of being precisely equal to 1,013,250 dynes per square centimeter (101,325 Pa). M^2 redirects here For other uses see M². CM2 redirects here This value is intended to represent the mean atmospheric pressure at mean sea level at the latitude of Paris, France, and as a practical matter, truly reflects the mean sea level pressure for many of the industrialized nations (those with latitudes similar to Paris). Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city

In chemistry, the original definition of “Standard Temperature and Pressure” (STP) was a reference temperature of 0 °C (273. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made The Celsius Temperature scale was previously known as the centigrade scale. 15 K) and pressure of 101. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic 325 kPa (1 atm). However, in 1982, the International Union of Pure and Applied Chemistry (IUPAC) recommended that for the purposes of specifying the physical properties of substances, “the standard pressure” should be defined as precisely 100 kPa (≈750. The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization 062 Torr). ^[1]

Contents 1 Pressure units and equivalencies 2 Other applications 3 See also 4 References

Pressure units and equivalencies

Pressure Units

	pascal (Pa)	bar (bar)	technical atmosphere (at)	atmosphere (atm)	torr (Torr)	pound-force per square inch (psi)
1 Pa	≡ 1 N/m2	10−5	1. The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. A technical atmosphere (symbol at is a non- SI unit of Pressure equal to one Kilogram-force per square centimeter The torr (symbol Torr) is a non- SI unit of Pressure defined as 1/760 of an atmosphere. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of The newton (symbol N) is the SI derived unit of Force, named after Isaac Newton in recognition of his work on Classical 0197×10−5	9. 8692×10−6	7. 5006×10−3	145. 04×10−6
1 bar	100,000	≡ 106 dyn/cm2	1. 0197	0. 98692	750. 06	14. 504
1 at	98,066. 5	0. 980665	≡ 1 kgf/cm2	0. The unit kilogram-force ( kgf, often incorrectly just kg) or kilopond ( kp) is defined as the Force exerted by Earth's gravity 96784	735. 56	14. 223
1 atm	101,325	1. 01325	1. 0332	≡ 1 atm	760	14. 696
1 torr	133. 322	1. 3332×10−3	1. 3595×10−3	1. 3158×10−3	≡ 1 Torr; ≈ 1 mmHg	19. The torr (symbol Torr) is a non- SI unit of Pressure defined as 1/760 of an atmosphere. 337×10−3
1 psi	6,894. 76	68. 948×10−3	70. 307×10−3	68. 046×10−3	51. 715	≡ 1 lbf/in2

Example reading:  1 Pa = 1 N/m²  = 10⁻⁵ bar  = 10. This article deals with the unit of force For the unit of mass see Pound (mass. 197×10⁻⁶ at  = 9. 8692×10⁻⁶ atm, etc.
Note:  mmHg is an abbreviation for millimetres of mercury.

A pressure of 1 atm can also be stated as:

≡1. 013 25 bar

≡101. The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. 325 kPa

≡1013. 25 millibars (mbar, also mb) or hectopascals (hPa)

≡760 torr ^[B]

≈760. The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure. The torr (symbol Torr) is a non- SI unit of Pressure defined as 1/760 of an atmosphere. 001 mm-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available ^{[B, C]}

≈29. 9213 in-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available ^[C]

≈1. 033 227 452 799 886 kgf/cm²

≈1. The unit kilogram-force ( kgf, often incorrectly just kg) or kilopond ( kp) is defined as the Force exerted by Earth's gravity 033 227 452 799 886 technical atmosphere

≈1033. A technical atmosphere (symbol at is a non- SI unit of Pressure equal to one Kilogram-force per square centimeter 227 452 799 886 cm–H₂O, 4 °C ^[A]

≈406. 782 461 732 2385 in–H₂O, 4 °C ^[A]

≈14. 695 948 775 5134 pounds-force per square inch (psi)

≈2116. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of 216 623 673 94 pounds-force per square foot psf)

Notes:

^A This is the customarily-accepted value for cm–H₂O, 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. VSMOW, or Vienna Standard Mean Ocean Water, is an isotopic water standard defined in 1968 by the International Atomic Energy Agency. 999 974 95 kg/l at 3. 984 °C). Also, this “physical realization” would still ignore the 8. 285 cm–H₂O reduction that would actually occur in a true physical realization due to the vapor pressure over water at 3. 984 °C.

^B Torr and mm-Hg, 0°C are often taken to be identical. For most practical purposes (to 5 significant digits), they are interchangeable.

^C NIST value of 13. 595 078(5) g/ml assumed for the density of Hg at 0 °C

Other applications

In the United Kingdom, scuba divers and others often use the word atmosphere loosely (the correct term is "ambient pressure") to mean 1 bar (1000 millibars, or 100 000 Pa). The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Scuba diving is swimming underwater, or taking part in another activity while using a Scuba set. The bar (symbol bar) decibar (symbol dbar) and the millibar (symbol mbar, also mb are units of Pressure.

The unit technical atmosphere (at) is roughly equal to the gauge pressure under 10 m of water; 1 at = 98066. A technical atmosphere (symbol at is a non- SI unit of Pressure equal to one Kilogram-force per square centimeter The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 5 Pa.

See also

• Standard conditions for temperature and pressure

References

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