Below line of code return all table’s size which associated with current database. Steps are given below

Use database

Syntax

USE <Database Name>
e.g.
USE MASTER

Copy and paste below line of code and execute query

USE MASTER 
SELECT CASE WHEN (GROUPING(sob.name)=1) THEN 'All_Tables'
   ELSE ISNULL(sob.name, 'unknown') END AS 'Table Name',
   SUM(sys.length) AS 'Size'
FROM sysobjects sob, syscolumns sys
WHERE sob.xtype='u' AND sys.id=sob.id
GROUP BY sob.name
WITH CUBE