Title: Avogadro constant
Long Title: IUPAC Gold Book - Avogadro constant
DOI: 10.1351/goldbook.A00543
Status: current
Index: constant

Definition
The Avogadro constant, \(N_{\rm{A}} = \pu{6.02214076E23 mol-1}\), is a proportionality constant between the quantity amount of substance (\(n\), with unit mole) and the quantity for counting entities (\(N\) with unit one, symbol 1), \(N = N_{\rm{A}}\ n\).

Notes
1) In the revision of the International System of Units (SI) of 2019 the Avogadro constant became one of the seven defining constants with the exact value \(\pu{6.02214076E23 mol-1}\).
2) The Avogadro number is the exact numerical value of the Avogadro constant, \(\pu{6.02214076E23}\)
3) While the symbol \(N_{\rm{A}}\) is used to honour Amedeo Avogadro, the symbol \(L\) is used in honour of Josef Loschmidt.

Related Terms
- amount of substance: https://goldbook.iupac.org//terms/view/A00297
- entities: https://goldbook.iupac.org//terms/view/N04266

Sources
- BIPM, Le Système international d’unités (SI), SI Brochure, 9e ed. (2019), p. 17 (https://www.bipm.org/fr/publications/si-brochure/)
- BIPM, The International System of Units, SI Brochure, 9th ed. (2019), p. 129 (https://www.bipm.org/en/publications/si-brochure/)
- Green Book, 3rd ed., p. 129 (https://doi.org/10.1039/9781847557889)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/A00543/html
- json: https://goldbook.iupac.org/terms/view/A00543/json
- xml: https://goldbook.iupac.org/terms/view/A00543/xml

Citation: Citation: 'Avogadro constant' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.A00543
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Accessed: 2026-04-28T20:37:02+00:00