question on wide of fabric
 

I am making a baby quilt. The wide of the fabric is too long. I need to applique circles on it. my question is should I wait until the quilt is finished and quilted before I cut the wide down or do I cut now it before I start the appliques.

I would leave it until after you applique the circles, unless it's too much fabric to manage under the arm of your sewing machine.

When you applique, the fabric will shrink slightly so I would do the applique and then trim down to the size you want. Be sure to measure twice and cut once.

if the backing is unwieldy, cut it down so it is about 4" larger than the front on each side.

If you only have a lot of excess fabric in one direction, I would cut it down. Applique work, especially circles, typically draw up the same amount of fabric from the width & the length. If you cut some off in advance, you can get a larger single cut that you could use in the future. Also, I personally find it easier to keep track of the layout if I don't have to try to picture it the same length, but much narrower.

I sell baby quilts &, in general, for whole cloth applique, I typically add 5-6" to the length and width of background fabric to account for needle turn work, hand embroidery & dense machine quilting. With whole cloth backgrounds, I buy a 60" cut of fabric (1 2/3 yd), which gives me a finished size of 36x54" (42" = WOF). At that size, I do not cut my background fabric until at least after I've finished the applique. At that point, I either physically square up my quilt with a rotary cutter so the sides are even & proportional (usually that's 39x57") or, more commonly, I measure from the center out (18" right & left of center; 27" above & below center) and mark the lines so I have a straight edge to work off of when quilting. Once I finish quilting, I cut to the desired finished size.