Proton mass in u
Atomic & nuclearMeasured
= 1.007 276 466 5789(83) u
- Value
- 1.007 276 466 5789 u
- Standard uncertainty
- 8.3 × 10−12 u
- Relative uncertainty
- 8.2 × 10−12 (8.2 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# proton mass in u, CODATA 2022 (NIST)
proton_mass_in_u = 1.0072764665789 # u, standard uncertainty 8.3e-12
# SciPy: scipy.constants.physical_constants['proton mass in u']What it is
The rest mass of the proton, the nucleus of the hydrogen atom, in unified atomic mass units (daltons), where 1 u is one twelfth of the mass of a carbon-12 atom.
In other units
| Unit | Value | |
|---|---|---|
| CGS (g) | 1.672 621 925 96 × 10−24 | |
| MeV/c² MeV / c² | 938.272 089 433 | |
| GeV/c² GeV / c² | 0.938 272 089 433 |
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 | 1.007 276 466 5789(83) | 8.2 × 10−12 | −0.8 σ of 2018 |
| 2018 | 1.007 276 466 621(53) | 5.3 × 10−11 | −2.8 σ of 2014 |
| 2014 | 1.007 276 466 879(91) | 9.0 × 10−11 | +0.7 σ of 2010 |
| 2010 | 1.007 276 466 812(90) | 8.9 × 10−11 | +0.4 σ of 2006 |
| 2006 | 1.007 276 466 77(10) | 9.9 × 10−11 | −0.8 σ of 2002 |
| 2002 | 1.007 276 466 88(13) | 1.3 × 10−10 | +0.0 σ of 1998 |
| 1998 | 1.007 276 466 88(13) | 1.3 × 10−10 |
“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).