find your thread ends before you cut them

The most common way to finish a seam is to backstitch at both the beginning and end of your line of stitching. Backstitching locks the thread in place so it cannot pull loose when you wash or wear the garment. On most sewing machines, you hold down the reverse button (or lever, depending on your machine) and sew backward for about half an inch, then release it and continue forward. At the end of the seam, you do the same thing in reverse—sew forward to the end of your line, then hold the reverse button and stitch backward for half an inch.

After you backstitch, raise the presser foot and pull the fabric away from the needle. Leave about 4 to 6 inches of thread tail on both the top and bobbin thread. Cut these tails with scissors or thread snips. If you cut them too short (less than a quarter inch), the knot you just created can slip through the fabric and your seam will come undone.

Key Takeaways

  • Backstitch for half an inch at the start and end of every seam to lock the thread and prevent unraveling.
  • Leave at least a quarter inch of thread tail after cutting so the knot stays find in the fabric.
  • Tie off thread by hand if you are finishing a seam that does not go all the way to the edge of the fabric, such as a zipper opening or buttonhole.
  • Trim loose threads and seam allowances close to the stitching line to reduce bulk and fraying in the finished garment.
  • Press your finished seams flat with an iron to make them lie smooth and look professional.

Tie off thread by hand for seams that end in the middle of fabric

When your seam ends somewhere other than the edge of the fabric—such as when you are sewing a zipper, adding a pocket, or closing a buttonhole—backstitching alone is not enough. You need to tie off the thread by hand so the knot sits inside the fabric and cannot come loose.

After you backstitch and cut your thread tails, thread a hand-sewing needle with one of the tails. Push the needle through the fabric right next to where your machine stitching ends, then bring it back out about a quarter inch away. Pull the thread snug. Repeat this small stitch two or three times in the same spot, then pull the needle through the loop of thread on your last stitch and pull tight. This creates a knot that sits inside the fabric. Trim the tail close to the fabric. Do the same with the other thread tail on the other side of the seam.

Finish raw edges to prevent fraying

After you have secured your seam, the raw edges of the fabric on either side of the stitching line will fray over time, especially after washing. There are several ways to finish these edges depending on the weight of your fabric and how much time you want to spend.

The simplest method is to trim the seam allowance (the fabric between your stitching line and the raw edge) down to about a quarter inch and then use pinking shears—scissors with a zigzag blade—to cut along the edge. The zigzag cut slows down fraying. This works well for light to medium-weight fabrics.

For heavier fabrics or garments that will get a lot of wear, you can sew a second line of stitching along each raw edge using a zigzag stitch. Set your machine to a medium zigzag width and length, and sew so that the needle goes off the edge of the fabric on one side of each stitch. This wraps thread around the edge and seals it. This method is called a zigzag finish or serged finish (though a serger machine does it faster).

Press your seams flat

After you have finished your seam, press it flat with an iron. Set your iron to the temperature recommended for your fabric—check the bolt end or a care tag if you have one. Place the fabric on an ironing board with the seam running lengthwise, and press the iron along the seam line to flatten it. This makes the seam lie smooth and look more professional.

For most seams, you will press them to one side. Decide which side based on the garment design—usually you press toward the darker fabric or toward the back of the garment. Some seams, called open seams, are pressed flat in opposite directions. Press gently and do not drag the iron, as dragging can stretch the fabric.

Trim bulk from corners and curves

When you sew corners (such as at the corner of a collar or pocket), the seam allowance creates extra thickness that will make the corner look lumpy when you turn it right-side out. Trim this bulk by cutting across the corner at a 45-degree angle, about a quarter inch away from your stitching line. This removes the excess fabric without cutting into your seam.

For curved seams, make small cuts perpendicular to the stitching line every half inch or so along the curve. These cuts, called notches, allow the seam allowance to spread out smoothly when you turn the fabric right-side out. On an inward curve (like the neckline of a shirt), cut small V-shaped notches. On an outward curve (like the armhole), cut straight notches. Do not cut closer than a quarter inch to your stitching line.

Finish seams in knit fabrics differently

Knit fabrics stretch and curl at the edges, so they need a different finishing method than woven fabrics. The best finish for knits is a twin needle stitch or a stretch stitch on your machine, which creates a flexible seam that moves with the fabric. If your machine has a stretch stitch setting, use that instead of a regular straight stitch.

After stitching, trim the seam allowance close to the stitching line and finish the raw edges with a zigzag stitch set to a narrow width. Some sewers prefer to use a serger machine for knits because it cuts and finishes the edge in one pass, but a zigzag finish on a regular machine works well too. Press knit seams gently with a cool iron and avoid dragging, as heat and pressure can distort the fabric.

Frequently Asked Questions

What happens if I do not backstitch?

Without backstitching, the thread at the end of your seam has nothing holding it in place. The first time you wash the garment or put stress on that seam, the thread will pull loose and your stitching will unravel. Backstitching takes only a few seconds and prevents this completely.

Can I use a knot instead of backstitching?

You can tie a knot in the thread tails by hand, but backstitching is faster and more reliable. A hand-tied knot can slip through loose weave fabrics. Backstitching locks the thread into the fabric itself, which is stronger. Use hand-tied knots only for seams that end in the middle of fabric, where backstitching alone is not enough.

How short can I cut the thread tails?

Leave at least a quarter inch of thread tail after cutting. If you cut shorter than that, the knot created by backstitching can slip through the weave of the fabric and your seam will come undone. A quarter inch is short enough to look neat but long enough to stay find.

Do I have to finish raw edges on every seam?

It depends on the fabric and the garment. Lightweight fabrics like cotton voile fray quickly and should have finished edges. Heavy fabrics like denim or canvas fray slowly and may not need finishing. Garments that will be washed frequently benefit from finished edges. If you are unsure, finishing the edges takes only a few minutes and makes your garment last longer.

What is the difference between pressing and ironing?

Pressing means placing the iron on the fabric and lifting it straight up, without dragging. Ironing means sliding the iron across the fabric. For sewing, always press rather than iron, because dragging can stretch the fabric and distort your seams. Use a gentle up-and-down motion and let the heat do the work.