A billiards table has a slate base, covered with green baize. Its length is always double its width. For major competition, the table is 5 by 10 or 4? by 9 feet; other sizes 4 by 8, and 3? by 7.The playing surface is 29? to 31 inches above the floor. Because of the cushions surrounding it, the actual playing surface is somewhat smaller than the overall dimensions of the table. On a 4? by 9 pool table, for example, the playing area is 50 by 100 inches.
http://www.hickoksports.com/rules/rbilliards.shtml
