# toBest() Function & Examples

Use the toBest() units function in Calcul.io. Review its syntax, edit working examples, understand the result, and explore related math functions.

## toBest

#### toBest(x)

#### toBest(x, unitList)

#### toBest(x, unitList, options)

Try it yourself:

```calculio
toBest(unit(5000, "m"))
toBest(unit(3500000, "W"))
toBest(unit(0.000000123, "A"))
toBest(unit(10, "m"), "cm")
toBest(unit(10, "m"), "mm,km", {offset: 1.5})
```

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## toBest(): choose a readable unit

**toBest(quantity)** converts a quantity to a unit that is convenient for people to read, often choosing a scale that avoids an awkward number of zeros.

## Presentation aid

A long duration may become minutes or hours; a small distance may become millimetres. The physical amount does not change, only the display unit.

## Related functions

Use [to()](https://calcul.io/function/to/index.md) when you require a specific unit, [format()](https://calcul.io/function/format/index.md) to choose decimal presentation, [round()](https://calcul.io/function/round/index.md) for displayed precision, and [numeric()](https://calcul.io/function/numeric/index.md) when an approximate number is required.

## Caveat

Automatic selection is convenient, but reports and APIs may need a fixed unit for consistency.

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