Tables sizes are determined by measuring between bumpers right where the ball would rebound from.
The red A line is the width of the table which is
usually half the length of the table, black line B.
Tables will vary in size by an inch or so, either
over or under. In which case check BOTH
length and width and compare to chart sizes.
Table size is whichever is closest to your measurement.
Below is a chart to help you figure out what size table you can fit in your room. Or maybe you have a table and need some short cues, this chart should help you with both!