What the Stefan-Boltzmann law describes
The Stefan-Boltzmann law states that the total energy radiated per unit surface area of an object is proportional to the fourth power of its absolute temperature. This means even small temperature increases dramatically increase radiated power — doubling temperature increases radiated power sixteen-fold.
The formula
Radiant emittance (power per unit area) is calculated as j = ε × σ × T⁴, where ε is emissivity (1 for a perfect black body, less for real materials), σ is the Stefan-Boltzmann constant (5.670374419 × 10⁻⁸ W/(m²·K⁴)), and T is absolute temperature in kelvin. Multiplying by surface area gives total radiated power in watts. The default values approximate the Sun’s photosphere temperature of about 5,778 K.
This calculator assumes a simplified black-body or gray-body radiator and does not account for surrounding environment reabsorption. This tool is for general educational and study purposes.