The biggest one was 10x10 feet (120 in.x 120in.) Calking on a Janome 6500. It was a lot.

I machine quilted a king-size bedspread in 2002 and vowed to never do anything like that again. It took me three weeks and I had to quilt it in three sections. My hands hurt so bad from trying to manipulate the quilt through the machine.

The biggest to date is a queen size. Once I got past the middle row, it really wasn't too bad. I roll the quilt on one side and also spray my sewing machine bed with silicone spray so it slides real easy.

wow, you go girl. I could not have done that. Congrats to those of you who have SUCCESSFULLY done the larger quilts. I can't get past a baby quilt

I've made many quilts for my 6'7" son-in-law and grandson so they are covered from head to toe,k. I divided them into three sections, quilt each section separate. When finished quilting I sew each top parts of the quilt by machine and the back by hand.

I have done 4 kings and several queens. The quilting was done following a specific design or meandering on all of them. It's not easy, but it can be done with a lot of patience and slowly. Can't hand quilt any more so have no choice. Can't afford a LAQ either.

I have done lap, full & queen size. The larger the quilt it gets a little troublesome but I can't afford to send it out. It all works out just need patience.

I am doing a queen size FMQ and its not easy true but I am still not believing that I am actually doing it. WOW I am making a music quilt for my DD and its been a chore but the results are still over amazing to my own eyes. So many have complimented me on this own design quilt that I still can't believe I can do this.
So answer to your question. Yes you can quilt any size by machine if you really have the patience and time.

I have done a 120x120 and it worked...hard. did it in half then sewed the two together.

I have done king size. A little difficult, until I got my juki. Now it's a breeze!