A full-size pingpong table is 9 feet long by 5 feet wide. Depending on you and your opponent's skill levels, much more room can be vital.
For beginners, only about 5 or 6 feet on all four sides of the table should be adequate but more would be preferred by most players.
For intermediate players, much more movement away from the table is experienced during game play. At least 8 feet behind the table and 5 feet to each side is a recommended minimum.
Advanced players can require excessive space once involved in intense game play with an advanced opponent. At least 12 feet behind the table and 6 to 7 feet on each side is probably acceptable.
Always remember you should have adequate space before investing in an expensive table. If you take playing seriously, then small spaces will only lead to frustration.
The playing space for Olympic pingpong is no less than 46 feet long and 23 feet wide, with plenty of ceiling space.