Tau mass = 3.167 54 × 10⁻²⁷ kg

Name: Tau mass — CODATA 2022 value
Creator: NIST

Value: 3.167 54 × 10⁻²⁷
Unit: kg
Uncertainty: 0.000 21 × 10⁻²⁷
Copy-ready: 3.16754e-27

Rest mass of the tau — the heaviest charged lepton, so short-lived it is only seen in collider decays.

Used to compute reaction energies, decay kinematics and binding energies. The lines below give the same mass in kilograms, atomic mass units (u), as an energy (mc², in J and MeV) and per mole, plus its ratio to other particles — all from the same CODATA adjustment, so they agree with each other.

The same quantity, other ways NIST lists it

Quantity (NIST name)	Value	Unit	Uncertainty
Tau-electron mass ratio	3477.23	(dimensionless)	0.23
Tau energy equivalent	1776.86	MeV	0.12
Tau mass energy equivalent	2.846 84 × 10⁻¹⁰	J	0.000 19 × 10⁻¹⁰
Tau mass in u	1.907 54	u	0.000 13
Tau molar mass	1.907 54 × 10⁻³	kg·mol⁻¹	0.000 13 × 10⁻³
Tau-muon mass ratio	16.8170	(dimensionless)	0.0011
Tau-neutron mass ratio	1.891 15	(dimensionless)	0.000 13
Tau-proton mass ratio	1.893 76	(dimensionless)	0.000 13

NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.

Particle masses

Alpha particle mass Deuteron mass Helion mass Muon mass Tau mass Triton mass

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