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The pascal (symbol: Pa) is the SI unit of pressure. It is equivalent to one newton per square meter, and was used in SI under that name before the name pascal was adopted by the 14th CGPM in 1971. 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 ㎩ (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.
Comparison to other units of pressure
Pressure Units
| |
Pascal
(Pa) |
Bar
(bar) |
Technical atmosphere
(at) |
Atmosphere
(atm) |
Torr
(mmHg) |
Pound per
square inch
(psi) |
| 1 Pa |
≡ 1 N/m² |
10−5 |
10.197×10−6 |
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 |
0.96784 |
735.56 |
14.223 |
| 1 atm |
101 325 |
1.01325 |
1.0332 |
≡ 101 325 Pa |
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 |
6 894.76 |
68.948×10−3 |
70.307×10−3 |
68.046×10−3 |
51.715 torr |
≡ 1 lbf/in² |
Example reading: 1 Pa = 1 N/m² = 10−5 bar = 10.197×10−6 at = 9.8692×10−6 atm ....etc.
Note: mmHg is an abbreviation for millimetres of mercury.
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|
This SI unit is named after Blaise Pascal. As for all SI units whose names are derived from the proper name of a person, the first letter of its symbol is uppercase (Pa). But when an SI unit is spelled out, it should always be written in lowercase (pascal), unless it begins a sentence or is the name "degree Celsius".
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See also
