Determine the free space available in MySQL DB

To determine size of database:

mysql>SELECT table_schema "Data Base Name",
sum( data_length + index_length ) / 1024 /
1024 "Data Base Size in MB",
sum( data_free )/ 1024 / 1024 "Free Space in MB"
FROM information_schema.TABLES
GROUP BY table_schema ;

ref:- MySQL Forums

To determine size of tables within a particular database:

mysql> SELECT table_name AS "Tables",
round(((data_length + index_length) / 1024 / 1024), 2) "Size in MB"
FROM information_schema.TABLES
WHERE table_schema = "$DB_NAME"
ORDER BY (data_length + index_length) DESC;