it depends on how you are quilting it- where there's a will, there's a way! some people manage to quilt some HUGE quilts on their domestic machines, some people choose to quilt large quilts in sections- then join the sections...and if you plan to send it to a long-arm quilter you need to check with the quilter- different long-arm quilters have different size tables/machines- the very first large quilt I made wound up being HUGE...as in 12 foot x 14 foot! (144" x 168"!) I took it to a long arm quilter---he did a fantastic job...and I paid ALOT! after that quilt I did really work at learning to make them stop growing.
