--- id: basics-dimensions title: Dimensions layout: docs category: The Basics permalink: docs/basics-dimensions.html next: basics-layout --- A component's dimensions determine its size on the screen. #### Fixed Dimensions The simplest way to set the dimensions of a component is by adding a fixed `width` and `height` to style. All dimensions in React Native are unitless, and represent density-independent pixels. ```ReactNativeWebPlayer import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class FixedDimensionsBasics extends Component { render() { return ( <View> <View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} /> <View style={{width: 100, height: 100, backgroundColor: 'skyblue'}} /> <View style={{width: 150, height: 150, backgroundColor: 'steelblue'}} /> </View> ); } }; AppRegistry.registerComponent('AwesomeProject', () => FixedDimensionsBasics); ``` Setting dimensions this way is common for components that should always render at exactly the same size, regardless of screen dimensions. #### Flex Dimensions Use `flex` in a component's style to have the component expand and shrink dynamically based on available space. Normally you will use `flex: 1`, which tells a component to fill all available space, shared evenly amongst each other component with the same parent. The larger the `flex` given, the higher the ratio of space a component will take compared to its siblings. > A component can only expand to fill available space if its parent has dimensions greater than 0. If a parent does not have either a fixed `width` and `height` or `flex`, the parent will have dimensions of 0 and the `flex` children will not be visible. ```ReactNativeWebPlayer import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class FlexDimensionsBasics extends Component { render() { return ( // Try removing the `flex: 1` on the parent View. // The parent will not have dimensions, so the children can't expand. // What if you add `height: 300` instead of `flex: 1`? <View style={{flex: 1}}> <View style={{flex: 1, backgroundColor: 'powderblue'}} /> <View style={{flex: 2, backgroundColor: 'skyblue'}} /> <View style={{flex: 3, backgroundColor: 'steelblue'}} /> </View> ); } }; AppRegistry.registerComponent('AwesomeProject', () => FlexDimensionsBasics); ```