Measure the distance between the side rails where the ball hits the cushion edge. Your table may vary up to +/- 3/4" from the correct measurements shown below.
If measurement is:

* 39" or 40"
44"
46"
50"
56"
69.5"
This is your Table Size:

7' table
8' table
8' pro table (oversize)
9' table
10' table
12' table