Get database/tables size

databases_size.sql

SELECT * 
FROM   (SELECT table_schema AS `DB Name`, 
           ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) AS `DB Size in MB`
        FROM   information_schema.tables 
        GROUP  BY `DB Name`) AS tmp_table 
ORDER  BY `DB Size in MB` DESC;

tables_size.sql

SELECT
  TABLE_NAME AS `Table Name`,
  ROUND((DATA_LENGTH + INDEX_LENGTH) / 1024 / 1024) AS `Size ( in MB)`
FROM
  information_schema.TABLES
WHERE
    TABLE_SCHEMA = "<db_name>"
ORDER BY
  (DATA_LENGTH + INDEX_LENGTH)
DESC;