Stefan-Boltzmann constant

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Physical constant
Surname Stefan-Boltzmann constant
Formula symbol
SI 5.670 374 419 ...e-8th
Uncertainty  (rel.) (exactly)
Relation to other constants

: Boltzmann constant : Planck's quantum of action : speed of light

Sources and Notes
Source SI value: CODATA 2018 ( direct link )

The Stefan-Boltzmann constant , after Josef Stefan and Ludwig Boltzmann , not to be confused with the Boltzmann constant , is a physical constant that occurs as a proportionality constant in the Stefan-Boltzmann law . According to this, the power of a black body emitted in the form of electromagnetic radiation is proportional to its surface area and the fourth power of its temperature :


The constants k B ( Boltzmann constant ), h ( Planck's quantum of action ) and c ( speed of light ) are used in the SI system to define the units of measurement and are assigned exact numerical values. This means that the Stefan-Boltzmann constant also has an exact value in the SI.


  1. a b The value of the Stefan-Boltzmann constant in SI units is exact , i.e. H. without measurement uncertainty, but due to the factor π 5 it has no finite representation of decimal places.