---
title: "FontScaling"
description: "Converts [TextUnit] to [Dp] and vice-versa.
If you are implementing this interface yourself on Android, please check the docs for important
optimization tips about caching."
type: "interface"
---
Interface
Common
```kotlin
@JvmDefaultWithCompatibility
expect interface FontScaling
```
Converts `TextUnit` to `Dp` and vice-versa.
If you are implementing this interface yourself on Android, please check the docs for important
optimization tips about caching.
## Properties
Common
```kotlin
val fontScale: Float
```
Current user preference for the scaling factor for fonts.
## Functions
```kotlin
open fun Dp.toSp(): TextUnit
```
Convert `Dp` to Sp. Sp is used for font size, etc.
```kotlin
open fun TextUnit.toDp(): Dp
```
Convert Sp to `Dp`.
Android
```kotlin
@JvmDefaultWithCompatibility
actual interface FontScaling
```
Converts `TextUnit` to `Dp` and vice-versa.
Note that the converter can't be cached in the interface itself. FontScaleConverterFactory
already caches the tables, but it still does a a map lookup for each conversion. If you are
implementing this interface, you should cache your own converter for additional speed.
## Properties
Android
```kotlin
actual val fontScale: Float
```
Current user preference for the scaling factor for fonts.
## Functions
```kotlin
actual fun Dp.toSp(): TextUnit
```
Convert `Dp` to Sp. Sp is used for font size, etc.
```kotlin
actual fun TextUnit.toDp(): Dp
```
Convert Sp to `Dp`.