# Rydberg Constant

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

## rydberg

Rydberg constant

Try it yourself:

```calculio
rydberg
```

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## Rydberg constant for spectral lines

**rydberg** is the Rydberg constant, which sets the characteristic wavenumber scale of hydrogen spectral transitions.

## Use

It appears in the Rydberg formula for wavelengths of hydrogen-like atoms. Combine it with [speedOfLight](https://calcul.io/constants/speedOfLight/index.md) to relate wavenumber to frequency and [planckConstant](https://calcul.io/constants/planckConstant/index.md) to relate frequency to photon energy.

## Caveats

Use the appropriate reduced-mass correction for real nuclei when precision matters. Wavenumber is inverse length, not frequency; use [divide](https://calcul.io/function/divide/index.md) with consistent SI units.

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