Boltzmann constant
The Boltzmann constant has an exact SI numerical value.
Key knowledge
The Boltzmann constant k is exactly 1.380 649 × 10⁻²³ J K⁻¹ by the SI definition.
Reference values
k1.380649e-23J K⁻¹
Exact value · SI definitionValues and equations
k = 1.380 649 × 10⁻²³ J K⁻¹
- k
- Boltzmann constant J K⁻¹
Conditions and scope
- The unit is joule per kelvin; temperature measurements retain uncertainty.
Sources · 4
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Bureau International des Poids et Mesures (BIPM)2 sources
- 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
BIPM defining-constant table; NIST Boltzmann value and kelvin definition.
2026-10-10 · Exact value, symbol and unit only; no particular thermal-energy formula is asserted.
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
Boltzmann’s constant has exact SI value 1.380649×10−23 J/K.
Exactness of the defining constant does not eliminate temperature-measurement uncertainty.
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 Kelvin, pp17–18
- 国際単位系(SI)第9版 · Japanese translation, V3.01
Entry details
Permanent link to this entry ↗- Record identity
- si-boltzmann-constant
- Revision
- core.1
- Structured reference record
- SI