Standard-state pressure
AdoptedExact
= 100 000 Pa
- Value
- 100 000 Pa
- Standard uncertainty
- exact
- Relative uncertainty
- exact
- Status
- Exact: IUPAC reference value
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
Plain
LaTeX
Python
# standard-state pressure, CODATA 2022 (NIST)
standard_state_pressure = 1e5 # Pa, exact
# SciPy: scipy.constants.physical_constants['standard-state pressure']What it is
The reference pressure for tabulated thermodynamic data recommended by IUPAC since 1982: exactly 100 kPa (1 bar), slightly below the standard atmosphere.
Equations
- definition
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm−1 g s−2) | 1 000 000 | exact |
| hPa hectopascal | 1000 | exact |
| kPa kilopascal | 100 | exact |
| MPa megapascal | 0.1 | exact |
| bar bar | 1 | exact |
| mbar millibar | 1000 | exact |
| atm standard atmosphere | 0.986 923 2667 | exact |
| Torr torr | 750.061 6827 | exact |
| mmHg millimetre of mercury | 750.061 5758 | exact |
| psi pound per square inch | 14.503 773 77 | exact |
| dyn/cm² dyne per square centimetre | 1 000 000 | exact |
Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display.
How the value changed, 1998–2022
| CODATA | Value (uncertainty) | Relative uncertainty | Change from previous |
|---|---|---|---|
| 2022 | 100 000 | exact | exact |
| 2018 | 100 000 | exact | exact |
| 2014 | 100 000 | exact | exact |
| 2010 | 100 000 | exact |
“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).