Loschmidt constant (273.15 K, 100 kPa)
Physico-chemicalExact
= 2.651 645 804… × 1025 m−3
- Value
- 2.651 645 804… × 1025 m−3
- Standard uncertainty
- exact
- Relative uncertainty
- exact
- Status
- Exact since the 2019 SI redefinition
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
NIST prints this exact value cut to 10 digits. ConstantID recomputes it from the defining constants: 2.651 645 804 883 734 342 411 204 695 24 × 1025…
Use in a calculation
# Loschmidt constant (273.15 K, 100 kPa), CODATA 2022 (NIST)
loschmidt_constant_273_15_k_100_kpa = 2.6516458048837343424112046952354978e25 # m^-3, exact
# SciPy: scipy.constants.physical_constants['Loschmidt constant (273.15 K, 100 kPa)']What it is
The number of molecules of an ideal gas in one cubic metre at 0 °C and 100 kPa (1 bar).
It is built only from constants that have exact values since 20 May 2019, so it is exact too; CODATA 2018 was the first adjustment to list it that way.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm−3) | 2.651 645 805 × 1019 | 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
Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart). Diamonds mark adjustments in which the value was exact.
Relative uncertainty
| CODATA | Value (uncertainty) | Relative uncertainty | Change from previous |
|---|---|---|---|
| 2022 | 2.651 645 804… × 1025 | exact | exact |
| 2018 | 2.651 645 804… × 1025 | exact | −0.6 σ of 2014 |
| 2014 | 2.651 6467(15) × 1025 | 5.7 × 10−7 | +0.2 σ of 2010 |
| 2010 | 2.651 6462(24) × 1025 | 9.1 × 10−7 |
“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).