# Pascal

For other uses, see Pascal (disambiguation).

The pascal (symbol: Pa) is the SI unit of pressure. It is equivalent to one newton per square metre. The same unit is also used for stress, Young's modulus, and tensile strength.

## Definition

1 pascal (Pa) = 1 N/m2 = 1 J/m3 = 1 kg·m–1·s–2

## SI multiples

Multiple Name Symbol Multiple Name Symbol
100 pascal Pa
101 decapascal daPa 10–1 decipascal dPa
102 hectopascal hPa 10–2 centipascal cPa
103 kilopascal kPa 10–3 millipascal mPa
106 megapascal MPa 10–6 micropascal µPa
109 gigapascal GPa 10–9 nanopascal nPa
1012 terapascal TPa 10–12 picopascal pPa
1015 petapascal PPa 10–15 femtopascal fPa
1018 exapascal EPa 10–18 attopascal aPa
1021 zettapascal ZPa 10–21 zeptopascal zPa
1024 yottapascal YPa 10–24 yoctopascal yPa

## Origin

The unit is named after Blaise Pascal, the eminent French mathematician, physicist, and philosopher.

## Explanation

1 megapascal (MPa) = 1 000 000 Pa = 1 N/mm2.

Standard atmospheric pressure is 101 325 Pa = 101.325 kPa = 1013.25 hPa = 1013.25 mbar = 760 Torr (ISO 2533).

Meteorologists worldwide have for a long time measured atmospheric pressure in millibars. After the introduction of SI units, many preferred to preserve the customary pressure figures. Therefore, meteorologists use hectopascals today for air pressure, which are equivalent to millibars, while similar pressures are given in kilopascals in practically all other fields, where the hecto prefix is hardly ever used.

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

In the former Soviet mts system, the unit of pressure is the pieze, which is equivalent to one kilopascal.

The Unicode computer character set has dedicated symbols ㎩ for Pa and ㎪ for kPa, but these exist merely for backward-compatibility with some older ideographic character sets.

## Comparison to other units of pressure

 1 bar 100 000 Pa 1 barye 0.1 Pa 1 millibar 100 Pa 1 atmosphere 101 325 Pa 1 mmHg (or Torr) 133.322 Pa 1 inHg 3386.833 Pa 1 cmH2O 98.0638 Pa
Pressure units and conversion factors
Pa bar at atm Torr psi
1 Pa ≡ 1 N/m² = 10−5 bar ≈ 10.2·10−6 at ≈ 9.87·10−6 atm ≈ 7.5·10−3 Torr ≈ 145·10−6 psi
1 bar = 100 000 Pa ≡ 106 dyn/cm² ≈ 1.02 at ≈ 0.987 atm ≈ 750 Torr ≈ 14.504 psi
1 at = 98 066.5 Pa = 0.980665 bar ≡ 1 kgf/cm² ≈ 0.968 atm ≈ 736 Torr ≈ 14.223 psi
1 atm = 101 325 Pa = 1.01325 bar ≈ 1.033 at ≡ 101 325 Pa = 760 Torr ≈ 14.696 psi
1 Torr ≈ 133.322 Pa ≈ 1.333·10−3 bar ≈ 1.360·10−3 at ≈ 1.316·10−3 atm ≡ 1 mmHg ≈ 19.337·10−3 psi
1 psi ≈ 6894.757 Pa ≈ 68.948·10−3 bar ≈ 70.307·10−3 at ≈ 68.046·10−3 atm ≈ 51.7149 Torr ≡ 1 lbf/in²