- Symbol
- σ
- Value
- 5.670 374 419... × 10−8
- Unit
- W·m⁻²·K⁻⁴
- Uncertainty
- exact (by definition)
- Copy-ready
5.670374419e-8
A black body radiates σT⁴ watts per square metre. The fourth power is why a small temperature rise changes radiated power so sharply.
NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.
Thermodynamic and chemical constants
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UsePhysics. "Stefan–Boltzmann constant — 5.670 374 419... × 10−8 W·m⁻²·K⁻⁴." UsePhysics.com. https://usephysics.com/reference/stefan-boltzmann-constant. Value from the 2022 CODATA adjustment (NIST). Accessed [date].