Bohr magneton
ElectromagneticMeasured
= 9.274 010 0657(29) × 10−24 J T−1
- Value
- 9.274 010 0657 × 10−24 J T−1
- Standard uncertainty
- 2.9 × 10−33 J T−1
- Relative uncertainty
- 3.1 × 10−10 (313 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
Plain
LaTeX
Python
# Bohr magneton, CODATA 2022 (NIST)
mu_B = 9.2740100657e-24 # J T^-1, standard uncertainty 2.9e-33
# SciPy: scipy.constants.physical_constants['Bohr magneton']What it is
The natural unit for the magnetic moment of an electron: the moment produced by one unit ħ of orbital angular momentum. The electron's own spin magnetic moment is very close to one Bohr magneton.
Equations
- definition
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).
Relative uncertainty
| CODATA | Value (uncertainty) | Relative uncertainty | Change from previous |
|---|---|---|---|
| 2022 | 9.274 010 0657(29) × 10−24 | 3.1 × 10−10 | −4.5 σ of 2018 |
| 2018 | 9.274 010 0783(28) × 10−24 | 3.0 × 10−10 | +1.5 σ of 2014 |
| 2014 | 927.400 9994(57) × 10−26 | 6.1 × 10−9 | +1.6 σ of 2010 |
| 2010 | 927.400 968(20) × 10−26 | 2.2 × 10−8 | +2.3 σ of 2006 |
| 2006 | 927.400 915(23) × 10−26 | 2.5 × 10−8 | −0.4 σ of 2002 |
| 2002 | 927.400 949(80) × 10−26 | 8.6 × 10−8 | +1.4 σ of 1998 |
| 1998 | 927.400 899(37) × 10−26 | 4.0 × 10−8 |
“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).