Atmosphere (unit) - Pressure Units and Equivalencies

Pressure Units and Equivalencies

Pressure units
	pascal	bar	technical atmosphere	standard atmosphere	torr	pound per square inch
	Pa	bar	at	atm	Torr	psi
1 Pa	≡ 1 N/m2	10−5	1.0197×10−5	9.8692×10−6	7.5006×10−3	1.450377×10−4
1 bar	105	≡ 106 dyn/cm2	1.0197	0.98692	750.06	14.50377
1 at	0.980665 ×105	0.980665	≡ 1 kp/cm2	0.9678411	735.5592	14.22334
1 atm	1.01325 ×105	1.01325	1.0332	≡ p₀	≡ 760	14.69595
1 Torr	133.3224	1.333224×10−3	1.359551×10−3	1.315789×10−3	≈ 1 mm_Hg	1.933678×10−2
1 psi	6.8948×103	6.8948×10−2	7.03069×10−2	6.8046×10−2	51.71493	≡ 1 lb_F/in2

A pressure of 1 atm can also be stated as:

≡1.013 25 bar

≡ 101325 pascal (Pa) or 1013.25 hectopascal (hPa)

≡ 1013.25 millibars (mbar, also mb)

≡ 760 torr

≈ 760.001 mm-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available

≈ 29.9213 in-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available

≈ 1.033 227 452 799 886 kgf/cm²

≈ 1.033 227 452 799 886 technical atmosphere

≈ 1033.227 452 799 886 cm–H₂O, 4 °C

≈ 406.782 461 732 2385 in–H₂O, 4 °C

≈ 14.695 948 775 5134 pounds-force per square inch (psi)

≈ 2116.216 623 673 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 0.999 974 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

D 14.696 = 1 atm Atmosphere (unit); at sea level 1 atm, human internal gravity is 1 atm

Read more about this topic: Atmosphere (unit)

Famous quotes containing the words pressure and/or units:

“We believe that civilization has been created under the pressure of the exigencies of life at the cost of satisfaction of the instincts.”
—Sigmund Freud (1856–1939)

“Even in harmonious families there is this double life: the group life, which is the one we can observe in our neighbour’s household, and, underneath, another—secret and passionate and intense—which is the real life that stamps the faces and gives character to the voices of our friends. Always in his mind each member of these social units is escaping, running away, trying to break the net which circumstances and his own affections have woven about him.”
—Willa Cather (1873–1947)