Hand-hemming a knit sweater works best for small adjustments

A hand-sewn hem on a knit sweater is the gentlest way to shorten the body or sleeves without a sewing machine. Unlike woven fabric, knits need a flexible stitch that moves with the fabric—a rigid seam will snap when you stretch the sweater. Hand-hemming takes 30 to 60 minutes depending on the length you're shortening, and the result is nearly invisible if you match your thread color.

This method works for hems up to about 2 inches shorter. If you need to remove more than that, the sweater's proportions may look off, and you risk cutting into ribbing at the cuffs or hem. For very large changes, a tailor with a serger (a machine that handles knits) is the safer choice.

Key Takeaways

  • Measure the sweater while wearing it or laying it flat against your body to find the right length before you cut.
  • Mark your cutting line with tailor's chalk or a fabric pen, then cut straight across—unraveling stitches one by one is slower and more error-prone than cutting.
  • Use a ballpoint or stretch needle with thread that matches your sweater color, and sew with a flexible stitch like the ladder stitch or running backstitch.
  • Test the stretch of your finished hem by pulling gently on the fabric; if the thread breaks or puckers, your stitch was too tight.

Measure twice before you cut

Put on the sweater and have someone mark where you want the new hem with a pin or piece of tape. Stand naturally—don't stretch upward or slouch. The hem should hit the same spot on your body as the original did, or where you prefer it to sit. If you're hemming alone, lay the sweater flat on a table and measure up from the original hem with a ruler.

Once you have your target length, add 1 inch for the fold-under. So if you want the sweater 2 inches shorter overall, you'll cut 3 inches up from the current hem. Write this measurement down so you don't forget it while you're working.

Cut the sweater straight across

Lay the sweater flat on a clean surface. Use a ruler or measuring tape to mark a line all the way around the sweater at your cut point. A tailor's chalk or fabric pen works best—pencil can smudge and regular pen may bleed through to the inside. Mark every 2 to 3 inches so you have a clear guide.

Cut along your marked line with sharp fabric scissors or a rotary cutter. Cut in one smooth motion rather than sawing back and forth, which can stretch the knit. If the edge curls up slightly after cutting, that's normal for knits—don't panic. You'll fold it under in the next step.

Fold and pin the new hem in place

Fold the cut edge up by 1 inch and pin it to the inside of the sweater. Use pins placed every 2 inches, perpendicular to the fold. The fold should be even all the way around—measure from the fold to the bottom edge of the sweater in several spots to check. If the edge curls, gently steam it or dampen it with a spray bottle and let it dry pinned in place for an hour.

Try on the sweater with the pins in place. The hem should sit where you want it and not pull or bunch. If it looks wrong, unpin and adjust before you sew.

Sew the hem with a flexible stitch

Thread a ballpoint needle (size 70/10 or 80/12) with thread that matches your sweater. Ballpoint needles slide between fibers rather than piercing them, which prevents runs in knits. If you don't have ballpoint needles, a stretch needle or universal needle works in a pinch.

The ladder stitch (also called the invisible stitch) is the best choice for knit hems because it's nearly invisible and very flexible. Bring your needle up through the fold, then across into the body of the sweater about 1/4 inch away. Go straight across inside the sweater for 1/4 inch, then back out through the fold. Repeat this pattern all the way around. Your stitches should be small and loose enough that you can slide your fingernail under the thread.

If ladder stitch feels too fiddly, a running backstitch also works: make small stitches (about 1/8 inch long) going in and out of the fold and the sweater body, staying about 1/4 inch from the fold line. Keep the tension loose—you should be able to stretch the sewn area gently without the thread pulling tight.

find the thread and remove pins

When you reach the end of your hem, bring the needle to the inside of the sweater and make three small stitches in the same spot to lock the thread. Weave the needle through a few stitches inside the sweater, then trim the thread close to the fabric. Remove all pins.

Try on the sweater and stretch the hem gently. If the thread holds and doesn't pucker, you're done. If you see puckering or the thread feels tight, you may need to go back and loosen some stitches by gently pulling the fabric away from the seam.

Common mistakes to avoid

The most common error is sewing too tightly. Knits need room to move, and a tight seam will snap or pucker when you wear and stretch the sweater. If you find yourself pulling the thread taut as you sew, you're working too tight—relax your grip and let the thread sit loose in the fabric.

The second mistake is cutting unevenly. A wavy or uneven cut line will show even after hemming. Use a ruler and mark your line clearly before you cut, and cut in one smooth motion rather than multiple passes.

Finally, don't skip the measuring step. Hemming is permanent, and cutting off too much is not fixable. Measure while wearing the sweater and double-check your math before you cut.

Frequently Asked Questions

Can I use a sewing machine to hem a knit sweater?

A regular sewing machine can work, but the seam often breaks when you stretch the sweater because the machine stitch is too rigid. If you use a machine, use a ballpoint needle, a stretch stitch setting (if your machine has one), and keep the tension very loose. Hand-sewing is safer for beginners.

What if my thread doesn't match the sweater color exactly?

Choose the closest match you can find—slightly darker is usually less visible than slightly lighter. If you're hemming a multicolor or patterned sweater, match the dominant color. The stitches will be hidden inside the fold anyway, so an exact match matters less than you might think.

How do I know if my hem is too tight?

Gently pull and stretch the hemmed area while wearing the sweater. If the thread feels like it's pulling the fabric or if you see puckering, the stitch is too tight. You can carefully cut a few stitches and re-sew them more loosely, or accept a slightly tighter hem if it doesn't bother you during wear.

Can I hem a sweater with ribbed cuffs or hem?

Yes, but only if you're shortening above the ribbing. Ribbed edges are stretchy and structural—cutting into them will cause unraveling. Measure carefully to make sure your cut line is at least 1/2 inch above any ribbing.

What should I do if I accidentally cut too much off?

Unfortunately, you cannot fix this by hemming. Once the fabric is cut away, it's gone. If you cut only a tiny bit too much (less than 1/4 inch), you might be able to fold the hem up an extra 1/4 inch, but this changes the sweater's proportions. In the future, cut conservatively and measure multiple times before cutting.