Proton mass
Atomic & nuclearMeasured
= 1.672 621 925 95(52) × 10−27 kg
- Value
- 1.672 621 925 95 × 10−27 kg
- Standard uncertainty
- 5.2 × 10−37 kg
- Relative uncertainty
- 3.1 × 10−10 (311 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# proton mass, CODATA 2022 (NIST)
m_p = 1.67262192595e-27 # kg, standard uncertainty 5.2e-37
# SciPy: scipy.constants.physical_constants['proton mass']What it is
The rest mass of the proton, the nucleus of hydrogen. It is about 1836.15 times the electron mass, and the neutron is heavier than it by 1.2933 MeV/c².
Equations
- rest energy
- nuclear magneton
In other units
| Unit | Value | |
|---|---|---|
| CGS (g) | 1.672 621 925 95 × 10−24 | |
| u dalton / atomic mass unit | 1.007 276 467 | unit is itself measured |
| MeV/c² MeV / c² | 938.272 089 428 | |
| GeV/c² GeV / c² | 0.938 272 089 428 |
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 | 1.672 621 925 95(52) × 10−27 | 3.1 × 10−10 | +4.4 σ of 2018 |
| 2018 | 1.672 621 923 69(51) × 10−27 | 3.0 × 10−10 | +1.2 σ of 2014 |
| 2014 | 1.672 621 898(21) × 10−27 | 1.3 × 10−8 | +1.6 σ of 2010 |
| 2010 | 1.672 621 777(74) × 10−27 | 4.4 × 10−8 | +1.7 σ of 2006 |
| 2006 | 1.672 621 637(83) × 10−27 | 5.0 × 10−8 | −0.3 σ of 2002 |
| 2002 | 1.672 621 71(29) × 10−27 | 1.7 × 10−7 | +1.0 σ of 1998 |
| 1998 | 1.672 621 58(13) × 10−27 | 7.8 × 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).