Curtains come in varying widths but there are limitations to the curtain sizes you can purchase off the shelf. These are made to fit the most common-size windows. If your home was made in another decade your windows may not be considered a standard size anymore. Also, if the home was custom built, the original owners may have had wider windows installed. You can save money when decorating your home by adding width to pre-made curtain panels instead of ordering custom made curtains.
Measure the width of your curtain rod. Include the returns in your measurement. The returns are the angled part of the rod from the bend back to the wall.
Measure your pre-made curtain panel. Subtract the curtain panel measurement from the rod measurement. Subtract an additional 2 inches for seam allowances. This is the amount of border needed to widen the curtain panel.
Divide the border amount by 2. This is the fabric width for each side border on your curtain panel.
Measure the finished length of your pre-made curtain. Measure the rod pocket fabric of the curtain. Measure the hem amount of the curtain. Add these three numbers together. This is the length of your border fabric.
Select a fabric that is similar in weight and texture to your current panels. Cut two pieces of border fabric to the fabric width and length measurements. Lay both border pieces face up, side by side. Turn the left edge of the left border piece under 1/2-inch. Turn another 1/2-inch. Pin the hem in place. Turn the right edge of the right border piece under 1/2-inch. Turn another 1/2-inch and pin the hem in place. Hem the bottom edge of both border fabrics to the same measurement as the pre-made curtain.
Lay the pre-made curtain flat with the right side up. Lay the left fabric on the curtain with the right side down. Align the bottom edge of the left fabric with the bottom edge of the pre-made curtain. The right edge of the border fabric will be lined up with the left edge of the pre-made curtain. Pin the two edges together. Machine stitch from the bottom edge and work up. Stop stitch 1-inch before you reach the rod pocket of the pre-made curtain.
Hand-stitch the remainder of the border fabric edge to the pre-made curtain. Do not sew the rod pocket closed. Sew the border fabric layer to the top layer of the curtain. Turn your border fabric to the back and continue stitching around the rod pocket. You will now be working from the back of the curtain. Hem the border fabric to match the rod pocket hem. Repeat for right border side.
Choose a contrasting colour between the border fabric and curtain. This will appear as a border rather than a poor attempt to colour match.
Using a heavier fabric than the curtains can cause your edges to hang in a sag.