The centipascal is a unit of pressure equal to one hundredth of a pascal. Its symbol is cPa. It is a legitimate metric combination that almost nobody writes, and understanding why it is unused says more about how pressure is actually recorded than a list of its applications ever could.
The centi prefix has one great success behind it, the centimetre, and that success came from the human scale of the metre. A metre is too long for the width of a hand and a millimetre too short, so the centimetre filled a real gap. Pressure has no comparable gap. The pascal is already so small that dividing it further gives numbers no instrument in ordinary use can resolve.
A centipascal is one hundredth of the pressure of a sheet of paper on a table. It is the pressure difference across a millimetre of air, or roughly what a grain of sand exerts spread over a fingernail. Nothing in engineering, meteorology or building practice needs that resolution: airtightness testing works at fifty pascals, ventilation at a few hundred, and weather at tens of thousands.
Where pressures smaller than a pascal do matter — acoustics and vacuum work — the convention jumps straight to the millipascal and the micropascal, because those fit the thousand-step ladder that the rest of the measurement system uses. A sound pressure of 20 millipascals is written that way rather than as 2 centipascals, even though the two are the same, because everything around it on the page is in thousand-step units.
The unit is nevertheless well defined, and that is the metric system working as designed. Every prefix combines with every unit without exception, so a reader who has never seen cPa can still decode it on sight from the prefix alone. A system with gaps would require a table; a system without them requires only the rule.
Occasional appearances do occur. Older instrument manuals sometimes use it, some national standards mention it in passing, and a few specialist fields adopt it locally when their numbers happen to fall between one and a hundred in that unit. A converter has to handle it for exactly those cases.
One centipascal equals 0.01 pascals, 10 millipascals, 0.1 decipascals, or about 0.00000145 pounds per square inch.
| Unit | Symbol | 1 Centipascal equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Nanopascal | nPa | 10000000 nPa | 0.0000001 cPa | Centipascals to Nanopascals |
| Micropascal | µPa | 10000 µPa | 0.0001 cPa | Centipascals to Micropascals |
| Millipascal | mPa | 10 mPa | 0.1 cPa | Centipascals to Millipascals |
| Decipascal | dPa | 0.1 dPa | 10 cPa | Centipascals to Decipascals |
| Pascal | Pa | 0.01 Pa | 100 cPa | Centipascals to Pascals |
| Newton per square meter | N/m² | 0.01 N/m² | 100 cPa | Centipascals to Newtons per square meter |
| Decapascal | daPa | 0.001 daPa | 1000 cPa | Centipascals to Decapascals |
| Hectopascal | hPa | 0.0001 hPa | 10000 cPa | Centipascals to Hectopascals |
| Kilopascal | kPa | 0.00001 kPa | 100000 cPa | Centipascals to Kilopascals |
| Bar | bar | 0.0000001 bar | 10000000 cPa | Centipascals to Bars |
| Megapascal | MPa | 0.00000001 MPa | 100000000 cPa | Centipascals to Megapascals |
| Gigapascal | GPa | 1 × 10-11 GPa | 100000000000 cPa | Centipascals to Gigapascals |
| Terapascal | TPa | 1 × 10-14 TPa | 100000000000000 cPa | Centipascals to Terapascals |
| Atmosphere | atm | 0.0000000986923266716 atm | 10132500 cPa | Centipascals to Atmospheres |
| Pound per square inch | psi | 0.0000014503773773 psi | 689475.729317 cPa | Centipascals to Pounds per square inch |
| Kilopound per square inch | ksi | 0.00000000145037743897 ksi | 689475700 cPa | Centipascals to Kilopounds per square inch |
| Megapound per square inch | Mpsi | 1.45037743897 × 10-12 Mpsi | 689475700000 cPa | Centipascals to Megapounds per square inch |