Stefan-Boltzmann Power Calculator

About this calculator

The Stefan-Boltzmann law, P = εσAT⁴, gives the total thermal power radiated by a surface as electromagnetic radiation, where σ is the Stefan-Boltzmann constant (5.670374×10⁻⁸ W/m²K⁴), A is the surface area, T is the absolute temperature in kelvin, and ε is the emissivity — a dimensionless factor from 0 to 1 describing how efficiently a real surface radiates compared to an ideal black body (ε = 1).

Because power scales with the fourth power of temperature, radiated heat loss grows extremely fast as an object gets hotter — this is why the law is central to designing incandescent filaments, furnace and kiln linings, spacecraft thermal control surfaces, infrared thermography, and climate models that balance the Earth's absorbed sunlight against its radiated heat loss to space.