Constants & Units · constant

Boltzmann constant

k_B = 1.380 649 × 10⁻²³ J K⁻¹

Unit

J K⁻¹

Value

1.380 649 × 10⁻²³

Exact

yes

Note

Fixes the kelvin. The exchange rate between temperature and energy per degree of freedom.

Symbol

k_B

Category

Defining (SI)

Numeric

1.380649e-23

Uncertainty

exact

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From the Constants database in Notion, last edited 2026-08-15. This page is the row, rendered by the build; nothing on it is written by hand.