# Planck Time Constant

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

## planckTime

Planck time

Try it yourself:

```calculio
planckTime
```

---

## Planck time: a natural interval

**planckTime** is the time light takes to travel one Planck length in vacuum. It is a natural unit derived from gravity, quantum mechanics, and relativity.

## Use

It provides a scale for theoretical models of the very early universe. It is linked directly to [planckLength](https://calcul.io/constants/planckLength/index.md) and [speedOfLight](https://calcul.io/constants/speedOfLight/index.md).

## Caveats

Planck time is not established as the smallest possible duration. Use SI seconds for experimental timing and [divide](https://calcul.io/function/divide/index.md) to make a deliberate unit conversion. It belongs with [planckTemperature](https://calcul.io/constants/planckTemperature/index.md) in Planck-unit estimates.

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