Helion mass = 5.006 412 7862 × 10⁻²⁷ kg

Name: Helion mass — CODATA 2022 value
Creator: NIST

Value: 5.006 412 7862 × 10⁻²⁷
Unit: kg
Uncertainty: 0.000 000 0016 × 10⁻²⁷
Copy-ready: 5.0064127862e-27

Rest mass of the helion — the nucleus of helium-3, two protons and one neutron.

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
Helion-electron mass ratio	5495.885 279 84	(dimensionless)	0.000 000 16
Helion mass energy equivalent	4.499 539 4185 × 10⁻¹⁰	J	0.000 000 0014 × 10⁻¹⁰
Helion mass energy equivalent in MeV	2808.391 611 12	MeV	0.000 000 88
Helion mass in u	3.014 932 246 932	u	0.000 000 000 074
Helion molar mass	3.014 932 250 10 × 10⁻³	kg·mol⁻¹	0.000 000 000 94 × 10⁻³
Helion-proton mass ratio	2.993 152 671 552	(dimensionless)	0.000 000 000 070
Helion relative atomic mass	3.014 932 246 932	(dimensionless)	0.000 000 000 074

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

Link to or cite this value

Link from a web page

Plain HTML for any page that accepts markup.

<a href="https://usephysics.com/reference/helion-mass">Helion mass — 5.006 412 7862 × 10−27 kg — UsePhysics</a>

Link from Markdown

For READMEs, wikis and notes.

[Helion mass — 5.006 412 7862 × 10−27 kg — UsePhysics](https://usephysics.com/reference/helion-mass)

Cite it in a document

Replace [date] with the day you consulted the page. The line credits NIST/CODATA for the values.

UsePhysics. "Helion mass — 5.006 412 7862 × 10−27 kg." UsePhysics.com. https://usephysics.com/reference/helion-mass. Value from the 2022 CODATA adjustment (NIST). Accessed [date].