Physics

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Stefan-Boltzmann Law Calculator.

Calculate emitted and net radiated power from a surface.

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Set your values

Results update as you type.

02 / ANSWER

Emissivity

Area

Surface temperature

Ambient temperature

Emitted power

0.000000W

Net radiated power

0.000000W

Results update automatically as you type.

Use Cases

Thermal design of radiators

Engineers use this calculator to estimate heat dissipation from radiators or heat sinks by inputting surface properties and operating temperatures.

Example: A radiator with emissivity 0.9, area 2 m², at 350 K in a 300 K room.

Astrophysics and planetary science

Researchers estimate radiation from celestial bodies or spacecraft components by treating them as gray bodies with known emissivity and temperatures.

Example: A satellite panel at 400 K with emissivity 0.8 and area 1.5 m².

Frequently Asked Questions

What does the Stefan-Boltzmann Law Calculator do?: This calculator computes the total power radiated by a surface (emitted power) and the net power exchanged with the surroundings (net radiated power) based on the Stefan-Boltzmann law. You input emissivity, surface area, surface temperature, and ambient temperature.
What units are required for temperature?: Both surface temperature and ambient temperature must be entered in Kelvin (K). The calculator uses absolute temperatures because the Stefan-Boltzmann law requires them for accurate results.
How is net radiated power different from emitted power?: Emitted power is the total radiation leaving the surface, while net radiated power accounts for radiation absorbed from the surroundings. Net power is the difference between emitted and absorbed radiation, indicating whether the surface heats or cools.

Tips & Common Mistakes

Tips

Ensure emissivity is between 0 and 1; typical values are 0.9 for matte black surfaces and 0.05 for polished metals.
Use Kelvin for all temperatures. Convert from Celsius by adding 273.15.
For accurate net power, ensure the ambient temperature represents the surrounding environment's effective radiation temperature.
Remember that the calculator assumes a uniform surface temperature and emissivity across the entire area.

Common Mistakes to Avoid

Forgetting to convert temperatures to Kelvin, leading to incorrect results.
Using emissivity values greater than 1 or negative, which are physically impossible.
Confusing emitted power with net power; net power is what determines heating or cooling.

Last updated: August 13, 2026

Use Cases

Thermal design of radiators

Engineers use this calculator to estimate heat dissipation from radiators or heat sinks by inputting surface properties and operating temperatures.

Example: A radiator with emissivity 0.9, area 2 m², at 350 K in a 300 K room.

Astrophysics and planetary science

Researchers estimate radiation from celestial bodies or spacecraft components by treating them as gray bodies with known emissivity and temperatures.

Example: A satellite panel at 400 K with emissivity 0.8 and area 1.5 m².

Frequently Asked Questions

What does the Stefan-Boltzmann Law Calculator do?

This calculator computes the total power radiated by a surface (emitted power) and the net power exchanged with the surroundings (net radiated power) based on the Stefan-Boltzmann law. You input emissivity, surface area, surface temperature, and ambient temperature.

What units are required for temperature?

Both surface temperature and ambient temperature must be entered in Kelvin (K). The calculator uses absolute temperatures because the Stefan-Boltzmann law requires them for accurate results.

How is net radiated power different from emitted power?

Emitted power is the total radiation leaving the surface, while net radiated power accounts for radiation absorbed from the surroundings. Net power is the difference between emitted and absorbed radiation, indicating whether the surface heats or cools.

Tips & Common Mistakes

Tips

Ensure emissivity is between 0 and 1; typical values are 0.9 for matte black surfaces and 0.05 for polished metals.
Use Kelvin for all temperatures. Convert from Celsius by adding 273.15.
For accurate net power, ensure the ambient temperature represents the surrounding environment's effective radiation temperature.
Remember that the calculator assumes a uniform surface temperature and emissivity across the entire area.

Common Mistakes to Avoid

Forgetting to convert temperatures to Kelvin, leading to incorrect results.
Using emissivity values greater than 1 or negative, which are physically impossible.
Confusing emitted power with net power; net power is what determines heating or cooling.

Use Cases

Thermal design of radiators

Engineers use this calculator to estimate heat dissipation from radiators or heat sinks by inputting surface properties and operating temperatures.

Example: A radiator with emissivity 0.9, area 2 m², at 350 K in a 300 K room.

Astrophysics and planetary science

Researchers estimate radiation from celestial bodies or spacecraft components by treating them as gray bodies with known emissivity and temperatures.

Example: A satellite panel at 400 K with emissivity 0.8 and area 1.5 m².

Frequently Asked Questions

What does the Stefan-Boltzmann Law Calculator do?

What units are required for temperature?

Both surface temperature and ambient temperature must be entered in Kelvin (K). The calculator uses absolute temperatures because the Stefan-Boltzmann law requires them for accurate results.

How is net radiated power different from emitted power?

Tips & Common Mistakes

Tips

Ensure emissivity is between 0 and 1; typical values are 0.9 for matte black surfaces and 0.05 for polished metals.
Use Kelvin for all temperatures. Convert from Celsius by adding 273.15.
For accurate net power, ensure the ambient temperature represents the surrounding environment's effective radiation temperature.
Remember that the calculator assumes a uniform surface temperature and emissivity across the entire area.

Common Mistakes to Avoid

Forgetting to convert temperatures to Kelvin, leading to incorrect results.
Using emissivity values greater than 1 or negative, which are physically impossible.
Confusing emitted power with net power; net power is what determines heating or cooling.