I long arm and usually can get by with 3" extra on all 4 sides. I find that if the backing is all squared up, then I can get by most times with 2" on all four sides--but it's a squeeze on the top and bottom with less than 3". The way I attach the sides allows the 2" on the sides though. But do check with your long arm quilter cause it does depend somewhat on the way it's attached to the frame.