# Vacuum Impedance Constant

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

## vacuumImpedance

Characteristic impedance of vacuum

Try it yourself:

```calculio
vacuumImpedance
```

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## Vacuum impedance of free space

**vacuumImpedance** is the characteristic impedance of electromagnetic waves in vacuum, expressed in ohms. It relates electric and magnetic field amplitudes of a freely propagating plane wave.

## Use

It is useful in antenna, radiation, and field calculations. It is related to the [electricConstant](https://calcul.io/constants/electricConstant/index.md), [magneticConstant](https://calcul.io/constants/magneticConstant/index.md), and [speedOfLight](https://calcul.io/constants/speedOfLight/index.md).

## Caveats

Vacuum impedance is not the resistance of a physical wire. Material wave impedance depends on the medium. Use [divide](https://calcul.io/function/divide/index.md) only with compatible field units and distinguish impedance from [conductanceQuantum](https://calcul.io/constants/conductanceQuantum/index.md).

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