Stefan-Boltzmann law

Total power emitted per unit area by a blackbody:

$$F=\sigma T^4$$

where:

• $F$: emitted flux (W m⁻²),
• $\sigma$: Stefan-Boltzmann constant, $5.67\times 10^{-8}$ W m⁻² K⁻⁴,
• $T$: temperature (K).

For a real (grey) body with emissivity $0\le \epsilon \le 1$:

$$F=\epsilon \sigma T^4$$