#### ${{\mathit p}}$ MASS (atomic mass units u)

The mass is known more precisely in u (atomic mass units) than in MeV. See the next data block.
VALUE (u) DOCUMENT ID TECN  COMMENT
 $\bf{ 1.007276466621 \pm0.000000000053}$ OUR EVALUATION  2018 CODATA
$1.007276466574$ $\pm0.000000000010$ 1
 2021
SPEC Penning trap
$1.007276466621$ $\pm0.000000000053$ 2
 2021
RVUE 2018 CODATA value
• • We do not use the following data for averages, fits, limits, etc. • •
$1.007276466598$ $\pm0.000000000033$ 3
 2019
SPEC Penning Trap
$1.007276466583$ $\pm0.000000000032$ 4
 2017
SPEC See HEISSE 2019
$1.007276466879$ $\pm0.000000000091$
 2016
RVUE 2014 CODATA value
$1.007276466812$ $\pm0.000000000090$
 2012
RVUE 2010 CODATA value
$1.00727646677$ $\pm0.00000000010$
 2008
RVUE 2006 CODATA value
$1.00727646688$ $\pm0.00000000013$
 2005
RVUE 2002 CODATA value
$1.00727646688$ $\pm0.00000000013$
 1999
RVUE 1998 CODATA value
$1.007276470$ $\pm0.000000012$
 1987
RVUE 1986 CODATA value
 1 FINK 2021 simultaneously measure the cyclotron frequencies of an ${{\mathit H}_{{2}}^{+}}$ ion and a deuteron in a coupled magnetron orbit. The proton mass is extracted using the precise deuteron mass value.
 2 The 2018 CODATA combination in TIESINGA 2021 includes data from HEISSE 2017 , but does not include updates in HEISSE 2019 , which superseded HEISSE 2017 . Consequently, we do not average HEISSE 2019 and TIESINGA 2021 . Updating the 2018 CODATA combination to use HEISSE 2019 would shift the central value for the proton mass upwards by less than half a standard deviation. Therefore, we take the 2018 CODATA result in TIESINGA 2021 as the recommended value for the proton mass.
 3 The value is an update of HEISSE 2017 ; the result is shifted by $1.5 \times 10^{-11}$ u, corresponding to 0.45 ${{\mathit \sigma}}$ due to the corrected motional temperatures of the particles. The statistical and total systematic uncertainties are given as 16 and 29 in the last two digits.
 4 The statistical and systematic errors are 15 and 29 in the last two places of the value. Superseded by HEISSE 2019 .
References:
 FINK 2021
PRL 127 243001
 TIESINGA 2021
RMP 93 025010 CODATA recommended values of the fundamental physical constants: 2018
 HEISSE 2019
PR A100 022518 High-precision mass spectrometer for light ions
 HEISSE 2017
PRL 119 033001 High-Precision Measurement of the Proton's Atomic Mass
 MOHR 2016
RMP 88 035009 CODATA Recommended Values of the Fundamental Physical Constants: 2014
 MOHR 2012
RMP 84 1527 CODATA Recommended Values of the Fundamental Physical Constants: 2010
 MOHR 2008
RMP 80 633 CODATA Recomended Values of the Fundamental Physical Constants: 2006
 MOHR 2005
RMP 77 1 NIST Constants
 MOHR 1999
JPCRD 28 1713 CODATA Recommended Values of the Fundamental Physical Constants: 1998;
 Also
RMP 72 351 CODATA Recommended Values of the Fundamental Physical Constants: 1998
 COHEN 1987
RMP 59 1121 CODATA Fundamental Physical Constants 1986 Adjustments