Natural unit of energy in MeV
UnitsMeasured
= 0.510 998 950 69(16) MeV
- Value
- 0.510 998 950 69 MeV
- Standard uncertainty
- 1.6 × 10−10 MeV
- Relative uncertainty
- 3.1 × 10−10 (313 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# natural unit of energy in MeV, CODATA 2022 (NIST)
natural_unit_of_energy_in_mev = 5.1099895069e-1 # MeV, standard uncertainty 1.6e-10
# SciPy: scipy.constants.physical_constants['natural unit of energy in MeV']What it is
The unit of energy in the natural units of relativistic quantum mechanics, where ħ, c and the electron mass are set to 1.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm2 g s−2) | 8.187 105 7879 × 10−7 | |
| eV electronvolt | 510 998.950 69 | |
| keV kiloelectronvolt | 510.998 950 69 | |
| Eₕ hartree | 18 778.865 07 | unit is itself measured |
| Ry rydberg | 37 557.730 14 | unit is itself measured |
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 | 0.510 998 950 69(16) | 3.1 × 10−10 | +4.6 σ of 2018 |
| 2018 | 0.510 998 950 00(15) | 2.9 × 10−10 | +1.3 σ of 2014 |
| 2014 | 0.510 998 9461(31) | 6.1 × 10−9 | +1.6 σ of 2010 |
| 2010 | 0.510 998 928(11) | 2.2 × 10−8 | +1.4 σ of 2006 |
| 2006 | 0.510 998 910(13) | 2.5 × 10−8 | −0.2 σ of 2002 |
| 2002 | 0.510 998 918(44) | 8.6 × 10−8 | +0.8 σ of 1998 |
| 1998 | 0.510 998 902(21) | 4.1 × 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).