Ditto to all of the above!
And yes, depends on what you mean by a full size quilt! And how much drop you want on the quilt.
The six repeats is minimal .... It's best to have a seventh, as most people include a strip of the original fabric somewhere on the quilt.
Or if you want to use the original fabric for borders and/or backing ... then more again!
I just did a OBW course ... we all had 12" repeats. One gal just barely had the six repeats and was doing a lap quilt. I had more than enough, and only did about 2/3 of the second set, in order to make it a larger quilt ... aiming for a large lap or double size. The 3rd girl is doing three repeats as she wants more of a bedspread size quilt.
We go back Friday for the put together session ... can't wait to see how everyone's has shaped up. Our fabrics are all so different!