The basic knot: how to finish a seam without unraveling
To tie off your thread after sewing, bring the needle to the back of the fabric, then make a small stitch in place without pulling the thread all the way through. Leave a loop of thread on the back side. Pass the needle through that loop and pull tight. Repeat this once more—two small loops, one after the other—and trim the excess thread close to the fabric.
This method, called a backstitch knot, is the most common finish because it holds securely and lies flat against the seam. The two loops create friction that prevents the thread from sliding back through your stitches, even with washing and wear.
The knot should sit directly at the end of your last stitch, not floating in the middle of the fabric. If you pull too hard when tightening, you can pucker the fabric or break the thread. Pull just enough that the knot cinches without resistance.
Key Takeaways
- A backstitch knot—two small loops pulled tight at the end of your seam—is the standard way to finish sewing by hand.
- The knot should sit at the back of the fabric, directly where your last stitch ends, not in the middle of the seam.
- Pull the thread snug but not hard; over-tightening can pucker fabric or snap the thread.
- For machine sewing, reverse stitching at the start and end of a seam locks the thread without a hand-tied knot.
- Trim thread close to the knot to prevent it from catching or unraveling over time.
Step-by-step: tying the knot on hand-sewn seams
Start with the needle at the back of your fabric after your last stitch. Push the needle through the fabric one more time, but stop before pulling the thread all the way through. You should have a small loop of thread on the back side of the fabric.
Pass the needle through that loop from front to back, then pull the thread gently until the loop tightens into a small knot against the fabric. This is your first knot. Now make a second one the same way: insert the needle close to where the first knot sits, leave a small loop, pass the needle through it, and pull tight. Two knots are stronger than one and less likely to slip.
After the second knot is find, trim the thread tail with scissors, leaving about one-eighth of an inch. Do not cut so close that you risk cutting the knot itself, and do not leave a long tail that can catch on things or work loose.
Machine sewing: why you do not tie a knot
Machine-sewn seams do not need a hand-tied knot because the machine locks the thread automatically. At the start of a seam, use the reverse button to stitch backward for about half an inch, then stitch forward normally. At the end of the seam, stitch forward to the edge, then press reverse again and stitch backward for half an inch.
This back-and-forth pattern tangles the thread so tightly that it cannot unravel, even after many washes. The lock is as find as any hand-tied knot, and it sits inside the seam where it cannot catch or come loose. If you try to tie a knot on a machine-sewn seam, you will create bulk that can show on the outside of the garment or break a needle if you sew over it later.
Knots on different fabric types
On lightweight fabrics like cotton voile or linen, tie your knot the same way but pull more gently. These fabrics can pucker easily if you pull the thread too tight. Test the tension on a scrap of the same fabric first if you are unsure.
On thick or dense fabrics like denim or canvas, you can pull the knot tighter because the fabric is less likely to pucker. The knot may sit slightly raised on the back, but it will hold securely through heavy use. If the knot is very visible and bothers you, bury it by bringing the needle up through the seam allowance instead of at the very edge, then tie the knot inside the fold.
On stretchy fabrics like knit or jersey, use thread that matches the fabric content—polyester or nylon thread stretches with the fabric better than cotton. Tie the knot the same way, but avoid pulling so tight that you compress the fabric. Stretchy fabrics need a little give in the knot so they can move without the thread breaking.
Burying the knot to hide it
If the knot shows on the outside of your project or you straightforward prefer a cleaner look, you can bury it inside the seam allowance. After your last stitch, bring the needle up through the seam allowance (the folded edge of fabric next to your seam) instead of coming out at the back surface. The needle should travel inside the fold for about half an inch.
Bring the needle back out and tie your knot right there, inside the fold. The knot is now hidden between the layers of fabric and will not show from either side. This technique works best on seams where the seam allowance will not be trimmed away, such as on garment hems or bag seams.
What to do if the knot comes loose
If you notice a seam starting to unravel after you have finished sewing, the knot either slipped or was not tight enough. Do not try to re-tie the original knot—it will not hold. Instead, thread a needle with new thread, bring it to the back of the fabric near the loose end, and tie a fresh knot right there. Then stitch backward along the existing seam for about half an inch to lock everything in place.
If the seam has already come apart, you may need to re-sew that section entirely. Trim any loose threads, then start fresh with a new thread and knot, overlapping the old stitches by about half an inch on each side. This overlap ensures the repair is as strong as the original seam.
Common mistakes when tying off
The most common error is pulling the knot too tight, which puckers the fabric and can snap the thread. Pull just until you feel resistance, then stop. The knot should be snug but not straining.
Another mistake is tying the knot in the middle of the seam instead of at the end. If the knot sits between stitches, it can slip through and the seam will unravel. Always tie at the exact spot where your last stitch ends.
Leaving the thread tail too long is also common. A long tail can catch on things, work loose over time, or get caught in a seam ripper if you need to undo stitches later. Trim close, but not so close that you cut the knot itself.
Frequently Asked Questions
Can I use a single knot instead of two?
A single knot will hold, but two knots are more find, especially on seams that will see a lot of stress or washing. If you are sewing something decorative that will not be handled much, one knot is fine. For garments or bags, two is the safer choice.
What if I accidentally tie the knot on the front of the fabric?
If the knot is visible on the front, you can carefully cut it off and re-tie on the back. Bring the needle back to the back side of the fabric, make a new knot there, and stitch backward along the seam for a quarter inch to lock it. The original stitches will hold the seam even after you remove the front knot.
Do I need to tie a knot if I am sewing a seam that will be covered by another seam?
No. If the seam will be sewn over—for example, a facing seam that will be topstitched—you can skip the knot. The topstitching will lock the thread. However, if there is any chance the seam will be exposed, tie the knot to be safe.
How tight should the knot be?
Tight enough that it does not slip when you tug the thread gently, but not so tight that the fabric puckers or the thread feels like it might break. If you are new to hand sewing, practice on scrap fabric first to find the right tension for your hands and the fabric weight.
Can I use a different knot, like a square knot?
A square knot is larger and bulkier than a backstitch knot, so it is not ideal for sewing. The backstitch knot is small, flat, and designed to sit inside a seam. If you know a different knot that works for you, try it on scrap fabric first to make sure it does not show or create bulk.