Calculator for Ideal Black Bodies
Calculate black body radiation with the Stefan-Boltzmann law
An ideal black body is a theoretical model for something which absorbs every incoming electromagnetic radiation. Practically, this model is used e.g. for stars and furnaces. The radiation of a black body can be calculated with the Stefan-Boltzmann law.
Please enter two values and select the units. The third value will be calculated.
The formula is P = σ * A * T4 with the Stefan-Boltzmann constant σ = 5,670367 * 10-8 W / m2 / K4
Example: the Sun with its surface area of 6087799000000 square kilometers and surface temperature of 5778 Kelvin has a radiant power of 384.75 yottawatts (YW, 1024 watts). The radiant power per square meter is 63.2 megawatts.
A black body or blackbody, so named in 1860 by Gustav Robert Kirchhoff, is also called a Planckian radiator after Max Planck. This is an idealized body that completely absorbs all incoming radiation. In this sense it is black, not only in visible light, but across the entire electromagnetic spectrum. Real bodies, in contrast, always reflect a certain portion of the radiation incident on them. A black body emits radiation that has nothing to do with the incoming radiation. This is because it has a temperature, i.e., it emits thermal radiation. At very low temperatures, this is microwave radiation; at temperatures we encounter in our environment, it is infrared radiation; and when the body is very hot, it glows, i.e., emits visible light. Even shorter-wavelength radiation is possible at higher temperatures. The emitted radiation extends in a left-sloping distribution over a certain range of the spectrum, with the maximum of this distribution being determined by the temperature.
A black body can be simulated by a cavity into which radiation can penetrate through a tiny hole but cannot escape. Therefore, blackbody radiation is also called cavity radiation.
Last updated on 06/30/2025. Author: Jürgen Kummer
Physics Calculators | © Jumk.de Webprojects | Online Calculators
Imprint & Privacy | German: Elektromagnetisches Spektrum
Retrieved on 2026-06-13 from https://rechneronline.de/spectrum/black-body.php