A React-Native utility belt for scaling the size of your apps UI across different sized devices.

npm install --save react-native-size-matters
//or:
yarn add react-native-size-matters

When developing with react-native, you need to manually adjust your app to look great on a variety of different screen sizes. That's a tedious job.
react-native-size-matters provides some simple tooling to make your scaling a whole lot easier.
The idea is to develop once on a standard ~5" screen mobile device and then simply apply the provided utils.
📖 You can read more about what led to this library on my blog post, which can be found in this repo or at Medium.

import { scale, verticalScale, moderateScale } from 'react-native-size-matters';

const Component = props =>
    <View style={{
        width: scale(30),
        height: verticalScale(50),
        padding: moderateScale(5)
    }}/>;

• scale(size: number)
  Will return a linear scaled result of the provided size, based on your device's screen width.

• verticalScale(size: number)
  Will return a linear scaled result of the provided size, based on your device's screen height.

• moderateScale(size: number, factor?: number)
  Sometimes you don't want to scale everything in a linear manner, that's where moderateScale comes in.
  The cool thing about it is that you can control the resize factor (default is 0.5).
  If normal scale will increase your size by +2X, moderateScale will only increase it by +X, for example:
  ➡️ scale(10) = 20
  ➡️ moderateScale(10) = 15
  ➡️ moderateScale(10, 0.1) = 11

All scale functions can be imported using their shorthand alias as well:

import { s, vs, ms } from 'react-native-size-matters';

import { ScaledSheet } from 'react-native-size-matters';

const styles = ScaledSheet.create(stylesObject)

ScaleSheet will take the same stylesObject a regular StyleSheet will take, plus a special (optional) annotation that will automatically apply the scale functions for you:

• <size>@s - will apply scale function on size.
• <size>@vs - will apply verticalScale function on size.
• <size>@ms - will apply moderateScale function with resize factor of 0.5 on size.
• <size>@ms<factor> - will apply moderateScale function with resize factor of factor on size.
• <size>@n - will keep the size intact, helpful when using with Config.awaysScale.

ScaledSheet also supports rounding the result, simply add r at the end of the annotation.

Example:

import { ScaledSheet } from 'react-native-size-matters';

const styles = ScaledSheet.create({
    container: {
        width: '100@s', // = scale(100)
        height: '200@vs', // = verticalScale(200)
        padding: '2@msr', // = Math.round(moderateScale(2))
        margin: 5
    },
    row: {
        padding: '[email protected]', // = moderateScale(10, 0.3)
        height: '50@ms' // = moderateScale(50)
    }
});

Sometimes you don't want to add annotation to the end of every number of your ScaledSheet because you want them to be scale automactically. In that case, you can you the Config object that we provide. Read below for more details.

In the ever-changing mobile devices world, screen sizes change a lot.
This lib uses 350dp x 680dp as guideline sizes, but if you (or your designer) prefer using different sizes it's possible.

To do so, first, you'd need to setup react-native-dotenv.
After setting it up and creating .env file, add the following env params to it:

SIZE_MATTERS_BASE_WIDTH=<custom-width>
SIZE_MATTERS_BASE_HEIGHT=<custom-height>

Next and final step, you should change all your imports to react-native-size-matters/extend, for instance:

import { ScaledSheet, moderateScale } from 'react-native-size-matters/extend';

If you want to change the default guideline sizes without adding react-native-dotenv lib to your app (you may prefer react-native-config), you can use the Config object to define the custom guideline sizes.

// sizeMattersConfig.js
import { Config } from 'react-native-size-matters'

Config.set({ guidelineBaseWidth: 375, guidelineBaseHeight: 812 }) // iphoneX

then import this file in your index.js or App.js file.

The Config object also accepts an alwaysScale attribute. If it's present, it will be applied to all the numeric values in ScaledSheet without any annotation required. To apply scale to ScaledSheet automatically, you can do something like this:

import { Config, scale } from 'react-native-size-matters'

Config.set({ alwaysScale: scale })

In case you want to disable scale on some values after you turn on alwaysScale, you can add postfix @n to that value. For example, the value in { margin: '10@n'} will not be scaled.

You can clone the expo-example-app from this repo, run npm install and npm start and scan the presented QR code in the Expo app on your preferred device.
The app has an on/off switch for using react-native-size-matters, so you can test yourself how the app will look with and without scaling.
It is expected to look good on every device you want - iOS or Android, phone or tablet, basically anything (please let me know if not).
There are also some attached screenshots in the repo if you don't feel like cloning.