Pascal (unit)

Pascal (unit)
A pressure gauge reading in psi (red scale) and kPa (black scale)
Unit information
Unit system: SI derived unit
Unit of... Pressure / Stress
Symbol: Pa
Named after: Blaise Pascal
In SI base units: 1 Pa = 1 kg/(m·s2)

The pascal (symbol: Pa) is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre. In everyday life, the pascal is perhaps best known from meteorological barometric pressure reports, where it occurs in the form of hectopascals (1 hPa ≡ 100 Pa) or kilopascals (1 kPa ≡ 1000 Pa).[1] In other contexts, the kilopascal is commonly used, for example on bicycle tire labels.[2] One hectopascal corresponds to about 0.1% of atmospheric pressure slightly above sea level; one kilopascal is about 1% of atmospheric pressure. One hectopascal is equivalent to one millibar; one standard atmosphere is exactly equal to 101.325 kPa or 1013.25 hPa or 101325 Pa. The correspondent Imperial unit is pounds per square inch (psi).



The pascal can be expressed using SI derived units, or alternatively solely SI base units, as:

{\rm 1~Pa = 1~\frac{N}{m^2} = 1~\frac{kg}{m \cdot s^2}}[3]

Where N is the newton, m is the metre, kg is the kilogram, and s is the second.

Pressure units
v · d · e 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 7.5006×10−3 145.04×10−6
1 bar 105 ≡ 106 dyn/cm2 1.0197 0.98692 750.06 14.5037744
1 at 0.980665 ×105 0.980665 ≡ 1 kp/cm2 0.96784 735.56 14.223
1 atm 1.01325 ×105 1.01325 1.0332 p0 760 14.696
1 Torr 133.322 1.3332×10−3 1.3595×10−3 1.3158×10−3 = 1 mmHg 19.337×10−3
1 psi 6.895×103 68.948×10−3 70.307×10−3 68.046×10−3 51.715 ≡ 1 lbF/in2


The unit is named after Blaise Pascal, the eminent French mathematician, physicist, and philosopher noted for his experiments with a barometer, an instrument to measure air pressure. The name pascal was adopted for the SI unit newton per square metre by the 14th CGPM in 1971. [1]

This SI unit is named after Blaise Pascal. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (Pa). When an SI unit is spelled out in English, it should always begin with a lower case letter (pascal), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.


Standard atmospheric pressure is 101,325 Pa = 101.325 kPa = 1013.25 hPa = 1013.25 mbar = 760 Torr[4] = 14.696 psi. This definition is used for pneumatic fluid power (ISO R554), and in the aerospace (ISO 2533) and petroleum (ISO 5024) industries.

In 1985 the IUPAC recommended that the standard for atmospheric pressure should be harmonized to 100,000 Pa = 1 bar = 750 Torr. The same definition is used in the compressor and the pneumatic tool industries (ISO 2787).

The Unicode computer character set has dedicated symbols (U+33A9) for Pa and (U+33AA) for kPa, but these exist merely for backward-compatibility with some older ideographic character-sets and are therefore deprecated.


The pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement is widely used throughout the world and largely replaces the pounds per square inch (psi) unit, except in some countries still using the Imperial measurement system.

Tectonophysicists use the gigapascal (GPa) in measuring or calculating tectonic forces within the earth.

In materials science, megapascals (MPa = N/mm2) or gigapascals (GPa = kN/mm2) are commonly used to measure stiffness or tensile strength of materials. Steel's tensile strength is approximately 200 GPa.

Other, older units of measure occasionally used for pressure are millimeters of mercury (Torr) and millimetres of water (1 mm H2O = 9.80665 Pa).

In the cgs system, the unit of pressure is the barye (symbol ba), which is equal to one decipascal. The older kilogram-force per square centimetre corresponds to 98.0665 kPa,[5] but is often rounded to 100 kPa in practice.

In the former mts system, the unit of pressure is the pièze (symbol pz), which is equal to one kilopascal.

Vehicle owners' guides now specify tire inflation in kilopascals.

Airtightness testing of buildings is measured at 50 Pa or 0.2 inches of water.[6]

Hectopascal and millibar units

Meteorologists worldwide have for a long time measured atmospheric pressure in bars, which was originally equivalent to the average air pressure on Earth; the bar was divided into a thousand millibars to provide the precision meteorologists require. After the introduction of SI units, many preferred to preserve the customary pressure figures. Consequently, the bar was redefined as 100,000 pascals, which is only slightly lower than standard air pressure on Earth. Today many meteorologists prefer hectopascals (hPa) for air pressure, which are equivalent to millibars, while similar pressures are given in kilopascals in practically all other fields, since the hecto prefix is rarely used. Since official metrication, meteorologists in Canada use kilopascals (kPa),[7][8] although in some other countries hectopascals are still in use.[9][10][11][12][13][14]

1 hectopascal (hPa) ≡ 100 Pa ≡ 1 mbar.
1 kilopascal (kPa) ≡ 1000 Pa ≡ 10 hPa ≡ 10 mbar.

See also


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Pascal (unite) — Pascal (unité) Pour les articles homonymes, voir Pascal …   Wikipédia en Français

  • Pascal — Contents 1 People 2 Things named after Blaise Pascal 3 Fictional characters …   Wikipedia

  • Pascal (name) — Infobox Given Name Revised name = Pascal imagesize= caption= pronunciation = pahs KALL gender = masculine meaning = associated with Easter (or Passover) region = origin = Hebrew related names = Pascale, Pascalle, Paschal, Paschalis, Pascoe,… …   Wikipedia

  • Pascal's law — In the physical sciences, Pascal s law or Pascal s principle states that a change in the pressure of an enclosed incompressible fluid is conveyed undiminished to every part of the fluid and to the surfaces of its container. [cite book last =… …   Wikipedia

  • Pascal (disambiguation) — Pascal or PASCAL may refer to:People* Pascal (name), a given name or surname * Blaise Pascal (1623–1662), French mathematician and philosopherFictional characters* Pascal, the main character in the film The Red Balloon * Pascal, a character in… …   Wikipedia

  • Pascal (programming language) — Pascal Paradigm(s) imperative, structured Appeared in 1970 Designed by Niklaus Wirth Typing discipline static, strong, safe …   Wikipedia

  • Unit — 〈[ ju:nıt] f. 10〉 1. 〈Päd.〉 Lerneinheit, Lernschritt (in Unterrichtsprogrammen) 2. (bei techn. Geräten) fertige Einheit 3. 〈allg.〉 Arbeitsgruppe, Team [engl., „Einheit“] * * * Unit [ ju:nɪt], die; , s [engl. unit, rückgeb. aus: unity < mengl.… …   Universal-Lexikon

  • Pascal Goldschmidt — Pascal J. Goldschmidt Clermont, M.D., is a Belgian born, American cardiologist, and is the Senior Vice President for Medical Affairs and the Dean of the Miller School of Medicine at the University of Miami. He was previously the Edward S. Orgain… …   Wikipedia

  • pascal — ► NOUN ▪ the SI unit of pressure, equal to one newton per square metre. ORIGIN named after the French scientist Blaise Pascal (1623 62) …   English terms dictionary

  • Pascal — Pascal1 [pas kal′] n. [after PASCAL2 Blaise] 1. a high level computer language, written in structured modules: also written PASCAL 2. [p ] the basic unit of pressure in SI and MKS systems, equal to the pressure of a force of one newton per square …   English World dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.