Reduced Planck constant = 1.054 571 817... × 10−34 J·s
- Symbol
- ℏ
- Value
- 1.054 571 817... × 10−34
- Unit
- J·s
- Uncertainty
- exact (by definition)
- Copy-ready
1.054571817e-34
h/2π. Exact by definition, but the decimal does not terminate — the trailing dots are NIST's, not a rounding.
NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.
Link to or cite this value
Link from a web page
Plain HTML. Works in any CMS, LMS or course page that accepts markup.
<a href="https://usephysics.com/reference/reduced-planck-constant">Reduced Planck constant — 1.054 571 817... × 10−34 J·s — UsePhysics</a>
Link from Markdown
For READMEs, wikis, Notion, Obsidian and static-site notes.
[Reduced Planck constant — 1.054 571 817... × 10−34 J·s — UsePhysics](https://usephysics.com/reference/reduced-planck-constant)
Cite it in a document
Replace [date] with the date you consulted the page. The constants themselves should be cited to NIST/CODATA — the line below does that for you.
UsePhysics. "Reduced Planck constant — 1.054 571 817... × 10−34 J·s." UsePhysics.com. https://usephysics.com/reference/reduced-planck-constant. Value from the 2022 CODATA adjustment (NIST). Accessed [date].