Oval is the most common shape for a poker table. The most common size oval tables are an 8-person 84″ x 42″ and a 10-person 94″ x 45″. Although these two sizes are the standard sizes, any size can be made to fit your space. All tables can also be made with folding legs or a permanent base.
Here are a few of each size –

Round Tables are also a popular shape and a lot of times a round table will better fit a game room space than a longer oval table.
Common sizes range from 48″ to 60″.