What this calculates
Every object above absolute zero radiates thermal energy. The Stefan-Boltzmann law quantifies how much power a body radiates based on its temperature, surface area, and emissivity (how close it behaves to a perfect blackbody emitter).
The formula
Radiated power P = ε × σ × A × T⁴, where ε is emissivity (1 for a perfect blackbody, less for real materials), σ is the Stefan-Boltzmann constant (5.670374419 × 10⁻⁸ W/(m²·K⁴)), A is surface area, and T is absolute temperature in kelvin.
This calculator is for general physics and engineering reference and education.
Last reviewed August 2026