MonitoringControl · Fundamental physics

CODATA physical-constant precision

Relative standard uncertainty across a fixed set of seven measured constants.

2022: 0.029536 ppb geometric mean uncertainty

1998
0.365348
2022
0.029536
Precision factor
12.37×
Constants / editions
7 / 7

Relative uncertainty by CODATA adjustment

CODATA physical-constant relative uncertainty Geometric mean and median relative standard uncertainty in parts per billion across seven fixed constants from 1998 through 2022. 0.0 0.1 0.2 0.3 0.4 1998 2002 2006 2010 2014 2018 2022 1998: 0.365348 ppb geometric mean 2002: 0.27539 ppb geometric mean 2006: 0.152219 ppb geometric mean 2010: 0.108504 ppb geometric mean 2014: 0.085966 ppb geometric mean 2018: 0.056507 ppb geometric mean 2022: 0.029536 ppb geometric mean 1998: 0.579202 ppb median 2002: 0.462924 ppb median 2006: 0.435694 ppb median 2010: 0.321084 ppb median 2014: 0.095047 ppb median 2018: 0.059908 ppb median 2022: 0.017428 ppb median
Geometric meanMedianRelative standard uncertainty, ppb · lower is more precise
Constant set+
  • inverse fine-structure constant
  • proton-electron mass ratio
  • muon-electron mass ratio
  • deuteron-proton mass ratio
  • neutron-proton mass ratio
  • Rydberg constant
  • electron g factor

Excluded exact SI constants: Avogadro constant, Boltzmann constant, Planck constant, elementary charge.

Edition values+
EditionGeometric mean ppbMedian ppbConstants
2022 0.029536 0.017428 7
2018 0.056507 0.059908 7
2014 0.085966 0.095047 7
2010 0.108504 0.321084 7
2006 0.152219 0.435694 7
2002 0.27539 0.462924 7
1998 0.365348 0.579202 7
Individual constants+
Constant1998 ppb2022 ppbPrecision factor
inverse fine-structure constant 3.648676 0.153244 23.81×
proton-electron mass ratio 2.124006 0.017428 121.88×
muon-electron mass ratio 30.468892 22.247126 1.37×
deuteron-proton mass ratio 0.205102 0.004202 48.81×
neutron-proton mass ratio 0.579202 0.399449 1.45×
Rydberg constant 0.007564 0.001094 6.92×
electron g factor 0.004095 0.00018 22.78×
Analysis and limits+

Analysis

Report edition-to-edition ratios and a log-linear descriptive trend in geometric mean relative uncertainty. With only seven editions, individual trajectories and exact observed values remain primary to interpretation.

  • Use the median rather than geometric mean
  • Remove each constant one at a time
  • Report every constant without aggregation
  • Compare 1998–2014 with 2018–2022 without extrapolating an annual rate
  • Retain adjustment-year spacing rather than treating editions as equally spaced

Limits

  • CODATA adjustments are discrete syntheses of correlated measurements rather than independent annual observations.
  • The fixed set emphasizes atomic, particle, and metrology constants and is not representative of all experimental physics.
  • The aggregate geometric mean can hide different trajectories among individual constants; all seven trajectories and the median remain visible.
  • Constants made exact through SI definition are excluded because zero uncertainty would reflect definition rather than improved measurement.
  • The series updates only when a new official CODATA adjustment is published and cannot resolve short-run changes in research productivity.
Data and sources+
Constant recordsObservationsSummarySource manifestDocumentationSource notice