Hi Angie, it will depend on the style of the handles and the style of your doors and drawers. If it's a modern kitchen with flat doors and drawers, using rod handles, then it's safe to go 3" from the sides. If your drawers are extra wide like in the image here, you will want to bring them in a bit more. The only thing I can see causing trouble is availability of handles of different lengths - generally handles come in limited sizes, and this then becomes your design constraint.