# Stefan Boltzmann Constant

Use Stefan Boltzmann in Calcul.io. See what this built-in constant represents, enter it in an editable calculation, and review related values and units.

## stefanBoltzmann

Stefan-Boltzmann constant

Try it yourself:

```calculio
stefanBoltzmann
```

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## Stefan–Boltzmann constant and thermal emission

**stefanBoltzmann** is the constant in the Stefan–Boltzmann law, which gives blackbody emitted power per area as proportional to the fourth power of absolute temperature.

## Use

Estimate ideal radiative power with σT⁴, often adjusted by emissivity. Compare [boltzmann](https://calcul.io/constants/boltzmann/index.md) and [secondRadiation](https://calcul.io/constants/secondRadiation/index.md) for related blackbody constants.

## Caveats

Real surfaces are not perfect blackbodies. Temperature must be in kelvin and the fourth power matters; use [pow](https://calcul.io/function/pow/index.md) with care and [multiply](https://calcul.io/function/multiply/index.md) for area and emissivity.

[All constants](https://calcul.io/constants/index.md)