Proton molar mass

$M(p)$ = 1.007 276 467 64(31) × 10⁻³ kg mol⁻¹

Value: 1.007 276 467 64 × 10⁻³ kg mol⁻¹
Standard uncertainty: 3.1 × 10⁻¹³ kg mol⁻¹
Relative uncertainty: 3.1 × 10⁻¹⁰ (308 parts per trillion)
Status: Measured
Symbol: $M(p)$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# proton molar mass, CODATA 2022 (NIST)
proton_molar_mass = 1.00727646764e-3  # kg mol^-1, standard uncertainty 3.1e-13

# SciPy: scipy.constants.physical_constants['proton molar mass']

What it is

The mass of one mole of protons (proton), in kilograms per mole.

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	1.007 276 467 64(31) × 10⁻³	3.1 × 10⁻¹⁰	+4.4 σ of 2018
2018	1.007 276 466 27(31) × 10⁻³	3.1 × 10⁻¹⁰	−6.7 σ of 2014
2014	1.007 276 466 879(91) × 10⁻³	9.0 × 10⁻¹¹	+0.7 σ of 2010
2010	1.007 276 466 812(90) × 10⁻³	8.9 × 10⁻¹¹	+0.4 σ of 2006
2006	1.007 276 466 77(10) × 10⁻³	9.9 × 10⁻¹¹	−0.8 σ of 2002
2002	1.007 276 466 88(13) × 10⁻³	1.3 × 10⁻¹⁰	+0.0 σ of 1998
1998	1.007 276 466 88(13) × 10⁻³	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).