---
title: "fillMaxSize"
description: "Have the content fill (possibly only partially) the [Constraints.maxWidth] and
[Constraints.maxHeight] of the incoming measurement constraints, by setting the
[minimum width][Constraints.minWidth] and the [maximum width][Constraints.maxWidth] to be equal
to the [maximum width][Constraints.maxWidth] multiplied by [fraction], as well as the
[minimum height][Constraints.minHeight] and the [maximum height][Constraints.minHeight] to be
equal to the [maximum height][Constraints.maxHeight] multiplied by [fraction]. Note that, by
default, the [fraction] is 1, so the modifier will make the content fill the whole available
space. If the incoming maximum width or height is [Constraints.Infinity] this modifier will have
no effect in that dimension."
type: "modifier"
---

<div class='type'>Compose Modifier</div>

<a id='references'></a>
<div class='sourceset sourceset-common'>Common</div>


```kotlin
fun Modifier.fillMaxSize(@FloatRange(from = 0.0, to = 1.0) fraction: Float = 1f) =
    this.then(if (fraction == 1f) FillWholeMaxSize else FillElement.size(fraction))
```


Have the content fill (possibly only partially) the `Constraints.maxWidth` and
`Constraints.maxHeight` of the incoming measurement constraints, by setting the
`minimum width` and the `maximum width` to be equal
to the `maximum width` multiplied by `fraction`, as well as the
`minimum height` and the `maximum height` to be
equal to the `maximum height` multiplied by `fraction`. Note that, by
default, the `fraction` is 1, so the modifier will make the content fill the whole available
space. If the incoming maximum width or height is `Constraints.Infinity` this modifier will have
no effect in that dimension.

#### Parameters

| | |
| --- | --- |
| fraction | The fraction of the maximum size to use, between `0` and `1`, inclusive. |




## Code Examples
### FillHalfSizeModifier
```kotlin
@Composable
fun FillHalfSizeModifier() {
    Box(Modifier.requiredSize(100.dp).background(Color.Red), contentAlignment = Alignment.Center) {
        // The inner Box will be (50.dp x 50.dp).
        Box(Modifier.requiredWidth(30.dp).fillMaxSize(0.5f).background(color = Color.Magenta))
    }
}
```
### SimpleFillModifier
```kotlin
@Composable
fun SimpleFillModifier() {
    Box(Modifier.fillMaxSize().background(Color.Red), contentAlignment = Alignment.Center) {
        Box(Modifier.size(100.dp).background(color = Color.Magenta))
    }
}
```