Calculate the total radiant heat power from a surface based on its temperature.
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About this calculator
Quick Reference
PRadiant power (Watts)
εEmissivity (0 to 1)
σ5.67 × 10^-8 W/(m²K⁴)
ASurface area (m²)
TTemperature (Kelvin)
Overview
The Stefan-Boltzmann Law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time is directly proportional to the fourth power of the black body's thermodynamic temperature.
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Pro Tips
The formula is P = ε * σ * A * T⁴.
Temperature must be in Kelvin (K).
ε (emissivity) ranges from 0 to 1 (1 for a perfect blackbody).
σ (Stefan-Boltzmann constant) is 5.670373 × 10^-8 W/(m²K⁴).
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Fun Facts
"This law is why you feel the heat from a campfire even if you aren't touching the flames or the hot air."
"The Sun's surface temperature is about 5,778 K; using this law, we can calculate its total energy output."
"Humans radiate about 100 Watts of power (mostly in the infrared), similar to an old incandescent light bulb."
