Cutout width is a term that has several definitions, depending on the activity in which one uses the term. The term can be applied whenever it is necessary to carefully map out an outline that needs to be cut out.
In fabric crafts, a cutout width is the space between the edge of the fabric and the outline of the shape you wish to cut out. For example, if you were cutting out material to sew, the cutout width is the extraneous part that you would use to fold over to make the seam. This is also called a seam allowance. For most fabrics, the width that you cut out is 5/8 of an inch.
The cutout width is a term used with other crafts as well, such as leatherworking, wood working, scrapbooking, foam or quilting. In these case, the cutout width of material can be recycled back into the project. For example, if you are quilting, the extra material might be used in edging the seam.
When remodeling, cutout width is the width of the empty space in which an appliance will be placed. The dimensions of the empty space are usually precut so that the appliance will fit directly into the space. The appliance itself should be slightly smaller so that it fits. The width of this space is referred to as a cutout width.
Regardless of what you are cutting out or what type of material you are cutting out, it is absolutely imperative that you measure carefully. The cutout width should be uniform on all sides. Be sure to read any directions or specifications for suggested cutout widths, as they vary depending on the project.