Stefan–Boltzmann Law

A law of thermal radiation stating that the total radiant energy emitted per unit surface area of a black body per unit time is proportional to the fourth power of its absolute temperature: j* = σ T^4, where σ is the Stefan–Boltzmann constant.

The total radiant exitance (power emitted per unit surface area) of a perfect blackbody is proportional to the fourth power of its absolute temperature: j* = σ T^4, where σ is the Stefan–Boltzmann constant; for real surfaces multiply by spectral- and direction-integrated emissivity to obtain emitted power.