How big a quilt can a long arm quilting machine handle?
What is the maximum width and length my quilt can be to be quilted on a longarm quilting machine?
The size of the frame the machine rides on determines the size of the quilt.
For instance a 14 foot frame will handle a quilt something smaller than 168 inches (14ft x 12in). The long arm quilter will somehow need to clamp the quilt from the sides and that will take up some space. That said, if you have a bed quilt that is 100" wide by 80" long or 80" wide by 100" long that the quilt would attach the quilt onto the rollers whichever way it fit the best.
The long armer you choose would be able to answer your question specifically with regards to her/his machine.
But I am not a long arm quilter, so I am unable to answer this question exactly.
Readers, if you own a long arm, please do share your experiences quilting large quilts on it with the 'comments' link below. Thank you!