What is the Stefan-Boltzmann constant?
The Stefan-Boltzmann constant is σ = 5.670374419e-8 W/(m^2·K^4), exact by SI definition. It governs blackbody radiation: power ∝ T^4.
Open the interactive PhysRef tool →Key facts
| Value | 5.670374419e-8 W m^-2 K^-4 |
|---|---|
| Symbol | σ |
| Law | P/A = σ·T^4 (blackbody) |
| Exactness | Exact by SI definition (uncertainty 0) |
| Source | CODATA 2018 |
Frequently asked questions
What is the value of the Stefan-Boltzmann constant?
σ = 5.670374419e-8 W/(m^2·K^4), the proportionality constant in the blackbody radiation law.
What is the Stefan-Boltzmann law?
The radiated power per unit area of a blackbody equals σ·T^4, so it rises steeply with temperature.
Is σ exact?
Yes. It is derived from exact constants (k_B, h, c) and is therefore exact.
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