react-native responsive

sizes.js

import { Dimensions } from 'react-native';

export const { height, width } = Dimensions.get('window');

const ratioX = width <= 375 ? (width <= 320 ? 0.75 : 0.875) : 1 ;
const ratioY = height <= 568 ? (height <= 480 ? 0.75 : 0.875) : 1 ;

const base_unit = 16;

const unit = base_unit * ratioX;

export const em = (value) => unit * value;
export const vh = (value) => (height/100) * value;
export const vw = (value) => (width/100) * value;