# Classical Electron Radius Constant

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

## classicalElectronRadius

Classical electron radius

Try it yourself:

```calculio
classicalElectronRadius
```

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## Classical Electron Radius

The **classicalElectronRadius** is a derived electromagnetic length scale for the electron. It is not the electron’s measured physical size.

## Interpret with care

It appears in scattering and classical electromagnetic formulas. Relate it to [elementaryCharge](https://calcul.io/constants/elementaryCharge/index.md), [electronMass](https://calcul.io/constants/electronMass/index.md), and [electricConstant](https://calcul.io/constants/electricConstant/index.md). Do not treat this classical parameter as a literal radius.

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