Atomic mass constant energy equivalent
Physico-chemicalMeasured
= 1.492 418 087 68(46) × 10−10 J
- Value
- 1.492 418 087 68 × 10−10 J
- Standard uncertainty
- 4.6 × 10−20 J
- Relative uncertainty
- 3.1 × 10−10 (308 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# atomic mass constant energy equivalent, CODATA 2022 (NIST)
atomic_mass_constant_energy_equivalent = 1.49241808768e-10 # J, standard uncertainty 4.6e-20
# SciPy: scipy.constants.physical_constants['atomic mass constant energy equivalent']What it is
The rest energy m_u c² of one atomic mass unit (one twelfth of a carbon-12 atom), in joules.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm2 g s−2) | 0.001 492 418 087 68 | |
| keV kiloelectronvolt | 931 494.103 714 | |
| MeV megaelectronvolt | 931.494 103 714 | |
| GeV gigaelectronvolt | 0.931 494 103 714 | |
| erg erg | 0.001 492 418 087 68 |
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. The relative uncertainty is unchanged by conversion to an exactly defined unit.
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 | 1.492 418 087 68(46) × 10−10 | 3.1 × 10−10 | +4.6 σ of 2018 |
| 2018 | 1.492 418 085 60(45) × 10−10 | 3.0 × 10−10 | +1.3 σ of 2014 |
| 2014 | 1.492 418 062(18) × 10−10 | 1.2 × 10−8 | +1.6 σ of 2010 |
| 2010 | 1.492 417 954(66) × 10−10 | 4.4 × 10−8 | +1.7 σ of 2006 |
| 2006 | 1.492 417 830(74) × 10−10 | 5.0 × 10−8 | −0.3 σ of 2002 |
| 2002 | 1.492 417 90(26) × 10−10 | 1.7 × 10−7 | +1.0 σ of 1998 |
| 1998 | 1.492 417 78(12) × 10−10 | 8.0 × 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).