- Symbol
- k
- Value
- 1.380 649 × 10−23
- Unit
- J·K⁻¹
- Uncertainty
- exact (by definition)
- Copy-ready
1.380649e-23
Defines the kelvin. The exchange rate between temperature and energy per particle. Often written kB.
NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.
The seven SI defining constants
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UsePhysics. "Boltzmann constant — 1.380 649 × 10−23 J·K⁻¹." UsePhysics.com. https://usephysics.com/reference/boltzmann-constant. Value from the 2022 CODATA adjustment (NIST). Accessed [date].