# Stefan-Boltzmann law - Power

## Description

The Stefan–Boltzmann law, also known as Stefan’s law, describes the power radiated from a black body in terms of its temperature. Specifically, the Stefan–Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time (also known as the black-body radiant exitance or emissive power) is directly proportional to the fourth power of the black body’s thermodynamic temperature T. To find the total power radiated from an object, multiply by its surface area.

Related formulas## Variables

P | total power radiated from an object (watt) |

A | area of the object (m^{2}) |

ϵ | emissivity of the grey body (dimensionless) |

σ | Stefan-Boltzmann constant |

T | black body's thermodynamic temperature (K) |