ConstantID

Tau molar mass

Atomic & nuclearMeasured

M(τ) = 1.907 54(13) × 10−3 kg mol−1

Value
1.907 54 × 10−3 kg mol−1
Standard uncertainty
1.3 × 10−7 kg mol−1
Relative uncertainty
6.8 × 10−5 (68 parts per million)
Status
Measured
Symbol
M(τ)
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# tau molar mass, CODATA 2022 (NIST)
tau_molar_mass = 1.90754e-3  # kg mol^-1, standard uncertainty 1.3e-7

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

What it is

The mass of one mole of taus (tau), 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).

tau molar mass: CODATA values 1998–2022 relative to the 2022 value, in parts per million, with one-standard-uncertainty bars−200−1000+100+200parts per million1998200220062010201420182022

Relative uncertainty

tau molar mass: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻⁵10⁻⁴10⁻³1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
20221.907 54(13) × 10−36.8 × 10−5 +0.0 σ of 2018
20181.907 54(13) × 10−36.8 × 10−5 +0.3 σ of 2014
20141.907 49(17) × 10−38.9 × 10−5 +0.0 σ of 2010
20101.907 49(17) × 10−38.9 × 10−5 −0.6 σ of 2006
20061.907 68(31) × 10−31.6 × 10−4 +0.0 σ of 2002
20021.907 68(31) × 10−31.6 × 10−4 −0.2 σ of 1998
19981.907 74(31) × 10−31.6 × 10−4

“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).

Related constants

Atomic & nuclear λ¯C,τ Reduced tau Compton wavelength 1.110 538(75) × 10−16 m Atomic & nuclear λC,τ Tau Compton wavelength 6.977 71(47) × 10−16 m Atomic & nuclear mτ/me Tau-electron mass ratio 3477.23(23) Atomic & nuclear mτc2 Tau energy equivalent 1776.86(12) MeV Atomic & nuclear mτ Tau mass 3.167 54(21) × 10−27 kg Atomic & nuclear mτc2 Tau mass energy equivalent 2.846 84(19) × 10−10 J Atomic & nuclear mτ Tau mass in u 1.907 54(13) u Atomic & nuclear mτ/mμ Tau-muon mass ratio 16.8170(11)