How to get the Width and Height of the Screen in Flutter?

You can get the width and height of the Screen through MediaQuery.Size property.
Here is the code snippet from which you can get the width and height of the screen of the phone.

final sizeX = MediaQuery.of(context).size.width;
final sizeY = MediaQuery.of(context).size.height;
 
Here is a sample example of how to use it in a program.
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Rows and Columns'),
        ),
        body: 
          Home(),
      ),
    );
  }
}

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final sizeX = MediaQuery.of(context).size.width;
    final sizeY = MediaQuery.of(context).size.height;
    return Container(
      color: Colors.red,
      width: sizeX,
      height: sizeY,
      child: 
      Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: <Widget>[
            Text('Width: $sizeX' ),
            Text('HeiGht: $sizeY' ),
        ],
      ) 
    );
  }
}

Hope this helps.
Thanks,
Srikanth