Thermal radiation converter
Convert a temperature into the power it radiates and the wavelength it peaks at. The power goes with the fourth power of temperature.
That's 1.04× as hot as the Earth’s surface, while a person is 1.03× hotter. It radiates about 459.3 W from every square meter.
What it means
How much does it radiate?
These are for a perfect black body. A real surface radiates its emissivity times as much — around 0.95 for skin and paint, 0.05 for polished metal.
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Three things worth knowing
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Double the temperature, sixteen times the power
A person at 310 K radiates 524 W/m²; a filament at 2,700 K radiates 3 megawatts per square meter. The fourth power is why heat loss runs away at high temperature.
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Guessed, then derived
Stefan found the fourth power in 1879 from other people’s measurements. His student Boltzmann derived it from thermodynamics five years later.
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Net loss is a difference
A person radiates 524 W/m² but a room at 20 °C radiates back about 420, so the net loss is far smaller. Forgetting the return term overstates cooling enormously.
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Background
About thermal radiation
Every object radiates, and the rate follows the fourth power of temperature: W/m² = 5.67 × 10⁻⁸ × T⁴. Doubling the temperature is sixteen times the power.
Wien’s law gives the color: the spectrum peaks at 2,898,000 ÷ T nanometers, which puts a person at 9.4 µm in the infrared and the Sun at 500 nm, in the green.