The basic method: backstitch and cut

To end a stitch on your sewing machine, sew forward to the end of your seam, then press the reverse button (or lever, depending on your machine) and sew backward over the last half-inch of stitches. This is called a backstitch, and it locks the thread so the seam won't unravel when you wash or wear the garment. After backstitching, raise the presser foot, pull the fabric away from the needle, and trim the thread tails with scissors or your machine's thread cutter.

The backstitch works because thread under tension wants to slip. When you stitch forward and then backward over the same spot, the two directions of thread lock against each other. Without it, the last few stitches will come loose the moment the seam experiences any pull.

Most machines have a reverse button on the front or a lever near the presser foot. Check your manual if you are not sure which—some older machines require you to hold the lever the entire time you backstitch, while newer ones lock into reverse when you press a button. Either way, you will hear or feel the machine shift into reverse, and the needle will move backward.

Key Takeaways

  • Backstitch by sewing in reverse over the last half-inch of your seam before cutting the thread, which prevents the stitches from unraveling.
  • Raise the presser foot before pulling the fabric away, or you risk bending the needle or breaking thread.
  • Trim thread tails close to the fabric so they do not get caught in later seams or show on finished edges.
  • Some seams, such as those in knit fabrics or stretch materials, may need a reinforced finish like a second backstitch or a zigzag stitch over the raw edge.
  • If your backstitch comes out loose or uneven, check that your thread tension is balanced and that you are using the correct needle size for your fabric.

When to backstitch and when to skip it

Backstitch at the end of almost every seam—the main exceptions are seams that will be crossed by another seam later, or seams that will be finished with a zigzag or serger. If you are sewing a side seam on a shirt, backstitch. If you are sewing a dart (a tapered seam that shapes fabric), backstitch. If you are attaching a pocket, backstitch.

The one time you should not backstitch is when you are sewing a seam that another seam will cross and lock in place. For example, if you sew the front and back panels of a shirt together, then sew the sleeves into the armholes, the sleeve seam will cross the shoulder seam and hold it in place. In that case, you can skip the backstitch on the shoulder seam because the sleeve seam will do the work. However, if you are uncertain, backstitch anyway—it takes five seconds and costs nothing.

How to backstitch on different machine types

On a standard domestic machine, the reverse button is usually a small square or rectangular button on the front panel, sometimes marked with an arrow pointing backward. Press it down and hold it while you sew backward, or press it once if your machine has a lock feature. Release it when you are done backstitching and you want to sew forward again.

On machines with a reverse lever instead of a button, the lever is typically located near the presser foot or on the side of the machine. You will need to hold the lever in the reverse position the entire time you are backstitching. Once you release it, the machine returns to forward sewing.

Some computerized machines have a button labeled "Tie Off" or "Lock Stitch" that automatically backstitches for you when you press it. If your machine has this feature, check your manual to see whether you need to press it at the start and end of a seam, or only at the end. A few machines can also be set to backstitch automatically whenever you stop sewing, which saves you from having to remember to do it by hand.

Trimming thread tails the right way

After you backstitch and raise the presser foot, gently pull the fabric away from the needle. The thread will pull free and you will see two tails—one from the top thread and one from the bobbin thread. Use scissors or your machine's built-in thread cutter to trim both tails as close to the fabric as you can without cutting the fabric itself. Leaving long tails can cause them to get tangled in the next seam or poke out from finished edges.

If your machine has a thread cutter, it is usually a small notch or blade on the presser foot or the back of the machine. Pull the thread tails toward the cutter and they will snap off. This is faster than scissors and leaves a very short tail, but it takes practice to aim correctly without pulling the fabric.

Some sewers leave a quarter-inch tail to tie off by hand later, especially on garments that will be washed frequently. This is optional—modern thread and machines hold seams well enough without hand-tying—but it is a common practice in tailoring and heirloom sewing.

Reinforcing seams that take a lot of stress

Seams on items that stretch or move a lot—like the crotch seam on pants, the underarm seam on a shirt, or any seam in a knit fabric—may benefit from a reinforced finish. One option is to backstitch twice: sew forward to the end, backstitch, then sew forward again to the end and backstitch a second time. This creates a thicker lock of thread that is harder to break.

Another option is to sew a short zigzag stitch over the raw edge of the seam after you have finished the straight stitch. This is called finishing the seam and it prevents fraying on woven fabrics and adds stretch to knit fabrics. You do not need to do this on every seam—it is most useful on seams that will be visible or that will experience a lot of movement.

If you are sewing with very stretchy fabric like swimsuit material or athletic wear, your machine manual may recommend using a ballpoint needle and a stretch stitch instead of a regular straight stitch. In that case, follow the manual's guidance on how to finish the seam, as a regular backstitch may break under the stress of the fabric.

Troubleshooting a loose or uneven backstitch

If your backstitch comes out loose or the stitches look uneven, the most common cause is incorrect thread tension. Check that both your top thread and bobbin thread are threaded correctly and that the tension dial is set to the middle position (usually marked as 4 or 5 on a scale of 1 to 9). If the top thread is too loose, the bobbin thread will show on top; if it is too tight, the top thread will bunch underneath.

Another cause of loose backstitches is using the wrong needle size or type for your fabric. A needle that is too small or too dull will not penetrate the fabric cleanly, and the thread will slip out of the needle eye as you sew. Replace the needle with a fresh one in the correct size for your fabric weight—for example, a size 70/10 needle for lightweight cotton, or a size 90/14 for medium-weight fabric.

If you are backstitching and the fabric bunches or puckers, you may be pulling the fabric toward you as you sew. Let the machine feed the fabric—do not guide it with your hands. If the problem persists, check that the presser foot is lowered all the way, because the foot must be down for the tension discs to grip the thread.

Frequently Asked Questions

Do I need to backstitch at the very beginning of a seam too?

Yes. Sew forward a few stitches, then backstitch to the start of the seam, then sew forward again to the end. This locks both ends. Some sewers skip the backstitch at the start if another seam will cross it, but backstitching at both ends is the safest habit.

What if I forget to backstitch and the seam starts to come undone?

You can fix it by hand. Thread a needle with matching thread, tie a knot at the end, and sew a few stitches backward and forward over the loose area. This will not look as neat as a machine backstitch, but it will hold the seam together.

Can I use the tie-off button instead of backstitching?

If your machine has an automatic tie-off or lock stitch button, yes. It does the same job as backstitching and is faster. Check your manual to see whether you need to press it at the start and end of each seam, or only at the end.

How short should I trim the thread tails?

Trim them as close to the fabric as you can without cutting the fabric itself—ideally a quarter-inch or less. Short tails are less likely to get caught in later seams or poke out from finished edges.

Do I need to backstitch on seams that will be hidden inside a garment?

Yes. Even hidden seams need to be locked so they do not unravel during washing and wearing. The only exception is a seam that will be crossed and held by another seam.