Planck constant
h denotes the Planck constant. Its numerical value is fixed exactly in SI units.
Key knowledge
h = 6.626 070 15 × 10⁻³⁴ J s, exactly by the SI definition.
Reference values
h6.62607015e-34J s
Exact value · SI definitionValues and equations
h = 6.626 070 15 × 10⁻³⁴ J s
- h
- h denotes the Planck constant. J s
Conditions and scope
- The value is expressed in joule seconds in the SI.
Exact definitions do not remove uncertainty from practical measurements.
Sources · 5
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Bureau International des Poids et Mesures (BIPM)3 sources
- SI defining constantsBureau International des Poids et Mesures (BIPM)Reference guide
- The International System of UnitsBureau International des Poids et Mesures (BIPM)Reference guide
- The International System of Units, 9th edition, version 4.01 (2026)Bureau International des Poids et Mesures (BIPM)Reference guide
- Meet the ConstantsNational Institute of Standards and Technology (NIST)Reference guide
- 国際単位系(SI)第9版 · Japanese translation, V3.01National Metrology Institute of Japan, AISTReference guide · PDF
Evidence and review
Exact SI value, symbol, unit and defining scope.
2026-10-09 · English value and scope checked against BIPM; value compared with NIST. This review covers the definition only.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
Planck’s constant has exact SI value 6.62607015×10−34 J s.
The national translation implements the same international defining constant.
National Metrology Institute of Japan, AIST
- 国際単位系(SI)第9版 · Japanese translation, V3.01 JapanJapaneseShared standard
2.2 Table1; 2.3.1 Kilogram, printed p16
- 国際単位系(SI)第9版 · Japanese translation, V3.01
Entry details
Permanent link to this entry ↗- Record identity
- si-planck-constant
- Revision
- 1
- Structured reference record
- SI