Muon mass energy equivalent in MeV

$m_μc²$ = 105.658 3755(23) MeV

Value: 105.658 3755 MeV
Standard uncertainty: 2.3 × 10⁻⁶ MeV
Relative uncertainty: 2.2 × 10⁻⁸ (22 parts per billion)
Status: Measured
Symbol: $m_μc²$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# muon mass energy equivalent in MeV, CODATA 2022 (NIST)
muon_mass_energy_equivalent_in_mev = 1.056583755e2  # MeV, standard uncertainty 2.3e-6

# SciPy: scipy.constants.physical_constants['muon mass energy equivalent in MeV']

What it is

The rest energy (mass × c²) of the muon, an unstable heavier cousin of the electron (about 207 times its mass) that lives about 2.2 microseconds, in mega-electronvolts, the unit particle physicists use.

In other units

Unit	Value
CGS (cm² g s⁻²)	1.692 833 804 × 10⁻⁴
keV kiloelectronvolt	105 658.3755
GeV gigaelectronvolt	0.105 658 3755
Eₕ hartree	3 882 873.682	unit is itself measured
Ry rydberg	7 765 747.364	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	105.658 3755(23)	2.2 × 10⁻⁸	+0.0 σ of 2018
2018	105.658 3755(23)	2.2 × 10⁻⁸	+0.4 σ of 2014
2014	105.658 3745(24)	2.3 × 10⁻⁸	+0.9 σ of 2010
2010	105.658 3715(35)	3.3 × 10⁻⁸	+1.2 σ of 2006
2006	105.658 3668(38)	3.6 × 10⁻⁸	−0.3 σ of 2002
2002	105.658 3692(94)	8.9 × 10⁻⁸	+2.4 σ of 1998
1998	105.658 3568(52)	4.9 × 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).