A bay window consists of three sections--a large window in the centre that is flanked by two smaller windows on each side. Because the unit sticks out of the wall, it typically has a seat or wide ledge. There are two basic ways to make curtains for this type of window: The first is to make individual pairs of curtains for each window. The second method is to make one large curtain that hangs in front of the entire unit, similar to a stage curtain. This application typically requires a larger curtain rod than the standard size required for three individual windows.
Measure each individual window opening or the entire bay window unit opening (depending on the style you choose) to determine the desired finished size of your curtain or curtains. Curtains for individual windows should end about 1 inch above the bay window seat or ledge. If you will be making one large curtain to go across the bay window opening, determine if you want the fabric to fall below the window seat or to skim on top of it.
For each opening (individual glass windows or full bay window unit opening), cut two pieces of curtain fabric. For width, each piece should be 1 1/2 times the width of the desired total finished width of the curtain. For example, if the opening is 50 inches wide, cut two pieces that each are 75 inches wide. Because bay windows can be quite large, you may need to piece two or more sections together. For length, measure the desired finished length from top to bottom and add 8 inches for standard-size rods and 12 inches for larger, decorative rods.
On each side of the curtain, fold under 1/2 inch to conceal raw edges and then fold over a 2-inch hem. Press and stitch down.
Make a top casing on the curtain fabric by folding under 1/2 inch to conceal raw edges and then folding down an additional 2 inches for standard-size rods and 4 inches for large rods. Press. Stitch 1/4 inch from both the top and bottom edges.
Make the bottom hem by folding under 1/2 inch to conceal raw edges and then folding up 3 inches. Press and stitch down.
Slip the curtains onto the rod, with the pieces meeting in the middle. Slide to open and close.
Curtain rod sizes vary. Before cutting fabric, measure the diameter of your curtain rod. Allow enough room for the rod to slide easily through the casing and add 1/2 inch for a seam allowance.
Always sew down the sides before making the top casing. Doing otherwise will close up the ends of the casing and prevent you from being able to slip the rod through.