How to Hem Curtains
To hem the bottom of your curtain, start by spreading it wrong-side-up on a flat surface. Then, fold the bottom of the curtain up the width you want the hem to be, and press it flat with an iron. Next, fold the hem up again by the same amount, and press it again. Finally, use iron-on hem tape to fuse the hem to your curtain. Alternatively, if you have a sewing machine, you can sew the hem. Just be sure to use thread that matches the color of your curtain, and sew the hem as close to the top folded edge as possible for the most professional look.
Make sure you have enough fabric for a double-folded hem. Curtain hems are folded twice at the bottom, so you will need twice as much fabric for the hem. This means that you will need to cut your curtains longer than you want them to be. The longer the curtain is, the wider the hem needs to be; this will help make it look more proportionate. Standard curtains have a 3 to 4 inch (7.62 10.16 centimeters) wide hem. You'll need to cut your curtains 6 to 8 inches (15.24 to 20.32 centimeters) longer than you want them to be. Shorter curtains might look better with a 2 inch (5.08 centimeter) wide hem. Cut your curtains 4 inches (10.16 centimeters) longer than you want them to be. Longer curtains, such as floor to ceiling, might look better with a 5 inch (12.7 centimeter) wide hem. Cut your curtains 10 inches (25.4 centimeters) longer than you want them to be. Spread the curtain, wrong-side-up on a flat surface. Because of their size, it might be easier to spread your curtains on the floor. If you have a very large table and a small curtain, however, you can work on the table. Fold your bottom up and press it flat with an iron. How far you fold it up depends on how wide you want your hem to be. For example, if you want a 4 inch (10.16 centimeters) wide hem, fold the bottom up by 4 inches (10.16 centimeters). Use sewing pins to hold the fabric in place while you iron it. Be sure to remove the pins when you are done ironing. Fold your hem up again and press it flat with an iron. Be sure that you are folding it up by the same amount as last time. For example, if you just folded your hem up by 4 inch (10.16 centimeters) earlier, fold it up by that same amount again. Pin the hem in place and press it flat with an iron. You have just folded your double hem. Keep the lining separate from the hem. The lining is usually hemmed on its own. It is tucked into the side hems, but not into the bottom hem. Click here to learn how to hem a curtain lining. Consider using iron-on hem tape to fuse the hem to the curtain. Cut a piece of hem tape slightly shorter than the width of your curtain. Slip it inside the hem, right between the back of the curtain and the folded hem. Align the top of the hem tape with the top of the folded hem. Iron the hem down. Press down with the iron for 10 seconds at a time before moving on to the next section. Most hem tapes will require a wool setting. Different brands will require different settings, however. Refer to the packaging from your hem tape for the proper setting. To prevent the fabric from burning, consider placing a damp cloth between the iron and the curtain. Some hem tapes have adhesive on one side, and a paper back on the other. You will need to iron it twice: first with the paper backing on, and then with the paper backing peeled off. You may find hem tape also labeled as stitch-witchery, iron-on hem tape, or fusible fabric tape. Consider using a sewing machine to sew the hem. Try to sew as close to the top folded edge as you can. Use a color that matches the curtain color as closely as possible. Make sure you have enough fabric for a double hem. Standard curtain panels have a 1½ inch (3.81 centimeters) wide hem on each side. The hem is folded twice, on both sides, so each panel will need to be 6 inches (15.24 centimeters) wider than you want them to be. This will allow you to create a double 1½ inch (3.81 centimeters) wide hem on each side. Fold each side of the curtain by 1½ inch (3.81 centimeters). The easiest way to do this would be to mark off 1½ inch (3.81 centimeters) at the top and bottom of your curtain, and then to fold it. Use sewing pins to hold the hem down. Fold the hem inward twice by 1½ inch (3.81 centimeters). Be sure to press the hem with an iron each time. If necessary, use sewing pins to hold the hem in place. Tuck the sides of the lining into the hem, if necessary. If your curtain has a lining, cut your lining down to the width of your curtain, then tuck the raw edges into the hem. Consider using iron-on hem tape to fuse the hem to the curtain. Cut a piece of hem tape slightly shorter than the length of your curtain. Slip it inside the hem. Align the edge of the hem tape with the edge of the folded hem. Iron the hem down. Consider using a sewing machine to sew the hem. Sew as close to the folded edge as you can. Be sure to use a color that matches the curtain color as closely as possible. Make sure you have enough fabric for a double-folded hem. The hem on a curtain lining should be 1 inch (2.54 centimeters) narrower than the hem on the curtain. For example, if your curtain has a 4 inch (10.16 centimeters) wide hem, the hem on the lining should be 3 inches (7.62 centimeters) wide. You'll need to cut your lining 6 inches (15.24 centimeters) longer than you want it to be. Curtain linings are about 1 inch (2.54 centimeters) shorter than the curtain. Plan accordingly. Undo part of the side hem, if necessary. Curtain linings are usually tucked into the side hem. If you are hemming a store-bought curtain, this could be a problem, depending on how short you are cutting and hemming your curtain. Use a seam ripper to undo the bottom portion of each side hem, and trim the lining down to the length you need. You will tuck it back into the side hems later. Fold the lining inside the curtain twice and press it flat with an iron. How much you fold it up will depend on how wide you want the hem to be. For example, if your hem to be 3 inches (7.62 centimeters), fold it up by 3 inches (7.62 centimeters). If necessary, use sewing pins to hold the hem in place. Be sure to remove the pins once you are done ironing. Make sure that you are folding the hem inside the curtain. You do not want the hem to be visible from the outside. The bottom edge of the lining should rest 1 inch (2.54 centimeters) above the bottom edge of the curtain when you are done. The bottom edges of the curtain and the lining should not be aligned. Consider using iron-on hem tape to fuse the hem to the lining. Cut a piece of hem tape slightly shorter than the width of your lining. Tuck it inside the hem, aligning the top edge with the top of the folded hem. Iron the hem down. Consider using a sewing machine to sew the hem. Try to sew as close to the top folded edge as you can. Use a color that matches the lining color as closely as possible. Sew the side hems down, if you unraveled them earlier. Be sure to tuck the lining into hem before you sew it down. Using hem tape for this would not be a good idea, especially if the rest of the side hem is sewn. You can sew it either by hand or on a sewing machine. Try to match the original thread color and stitch length as best as you can. 
Make sure you have enough fabric for a double-folded hem. Spread the curtain, wrong-side-up on a flat surface. Fold your bottom up and press it flat with an iron. Fold your hem up again and press it flat with an iron. Keep the lining separate from the hem. Consider using iron-on hem tape to fuse the hem to the curtain. Consider using a sewing machine to sew the hem. Make sure you have enough fabric for a double hem. Fold each side of the curtain by 1½ inch (3.81 centimeters). Fold the hem inward twice by 1½ inch (3.81 centimeters). Tuck the sides of the lining into the hem, if necessary. Consider using iron-on hem tape to fuse the hem to the curtain. Consider using a sewing machine to sew the hem. Make sure you have enough fabric for a double-folded hem. Undo part of the side hem, if necessary. Fold the lining inside the curtain twice and press it flat with an iron. Consider using iron-on hem tape to fuse the hem to the lining. Consider using a sewing machine to sew the hem. Sew the side hems down, if you unraveled them earlier. 