The basic approach: take in the side seams

The fastest way to make a shirt smaller is to take in the side seams — the vertical seams that run from armpit to hem on both sides of the shirt. This works because you can adjust the fit without touching the neckline, sleeves, or shoulders, which are harder to alter. You remove fabric equally from both sides so the shirt stays centered on your body.

Start by putting the shirt on inside-out and pinching the extra fabric on one side until the fit looks right. Have someone mark that line with tailor's chalk or a fabric pen, or use a mirror and mark it yourself. Measure how much you pinched — if you pinched one inch on each side, you are removing two inches total from the shirt's width. Repeat on the other side seam to keep the shirt balanced.

Sew a new seam along your marked line, then try the shirt on again before cutting. Once you confirm the fit, trim the old seam allowance down to about half an inch and finish the raw edge with a zigzag stitch or pinking shears so it does not fray.

Key Takeaways

  • Taking in the side seams is the simplest alteration because you adjust width without changing the neckline, sleeves, or shoulder fit.
  • Mark the new seam line while wearing the shirt inside-out, then sew and try it on before trimming the old seam away.
  • Remove the same amount from both sides so the shirt hangs straight and centered on your body.
  • Finishing the raw edges with a zigzag stitch or pinking shears prevents fraying and makes the alteration last longer.
  • If the shirt is too big in the shoulders or sleeves, taking in the sides alone will not fix those problems — you will need to adjust those seams separately.

When to take in the shoulders instead

If the shoulder seams sit too far out on your arms, taking in the sides will not help — the shirt will still hang wrong. In this case you need to move the shoulder seams inward. This is a more involved alteration because the sleeves are attached at the shoulders, so you have to unpick the sleeve seams, move the shoulder seam, and reattach the sleeves.

Mark the new shoulder line by putting the shirt on inside-out and pinching until the seam sits at the edge of your shoulder bone. Have someone mark it with chalk. Unpick the sleeve seams on both sides using a seam ripper, then sew the new shoulder seam and reattach the sleeves. This alteration is worth doing only if the shoulders are the main problem — if the shirt is also too wide in the body, take in the sides first and see if you still need to move the shoulders.

Shortening the sleeves

Sleeves that are too long are the easiest single alteration. Try the shirt on and have someone mark where the sleeve should end — usually at your wrist bone when your arm hangs at your side. Add half an inch for a seam allowance and cut the sleeve to that length.

Fold the raw edge under by half an inch, then fold it under again by another half inch, and sew it down with a straight stitch close to the inner fold. This creates a clean hem that looks professional. If the sleeve is very thick or has a cuff, you may need to unpick the cuff first, shorten the sleeve, and reattach the cuff — check whether your shirt has a sewn cuff or a folded hem before you cut.

Taking in the waist with darts or side seams

If the shirt is too loose around the middle but fits well in the shoulders and chest, you can add darts at the back or front to pull in the waist. A dart is a triangular fold of fabric that you sew closed — it removes fabric gradually rather than all at once, so the shirt still drapes naturally.

To add a back dart, put the shirt on inside-out and pinch the extra fabric at the center back, roughly at your waist level. Mark a line from that point down to the hem and back up to create a triangle, then sew along those lines. Start at the top of the triangle and sew toward the point, then backstitch to find. Trim the excess fabric inside the dart and press it flat.

If you prefer not to add darts, you can take in the side seams more at the waist than at the chest and hem — this creates a gradual taper that follows your body shape. Mark the new seam line so it is closer to the body at the waist and wider again at the hips and hem.

Dealing with thick fabrics and knits

Cotton shirts and woven fabrics are straightforward to alter because they hold a crease and do not stretch. Knit shirts — including t-shirts, jersey, and stretch cotton blends — require a different approach because they move and can curl at the edges.

For knits, use a ballpoint needle on your machine, which slides between fibers instead of piercing them and causing runs. Sew with a slight zigzag stitch rather than a straight stitch so the seam can stretch with the fabric. When you trim the seam allowance, leave it a bit wider than you would on woven fabric — about three-quarters of an inch — and finish it with a zigzag or a serger if you have one. If the fabric is very stretchy, consider using a twin needle, which creates a professional-looking stretch seam that moves with the shirt.

Checking the fit before you cut

The most common mistake is cutting away the old seam before you have sewn and tested the new one. Always sew your new seam first, try the shirt on, and confirm the fit looks right and feels comfortable. Only then should you trim away the old seam and finish the raw edge.

If you sew and the fit is not quite right, you can unpick that seam and try again — the fabric is still there. Once you cut it away, you cannot get it back. Leave yourself at least half an inch of seam allowance on the old seam so you have room to adjust if needed.

Frequently Asked Questions

Can I make a shirt smaller if it is too big in the shoulders?

Yes, but it requires moving the shoulder seams inward, which means unpicking and reattaching the sleeves. This is more work than taking in the sides. If the shoulders are only slightly too wide, try taking in the side seams first — sometimes that alone makes the fit acceptable.

What thread should I use?

Match the thread color to the fabric, not the thread the shirt was originally sewn with. Use all-purpose polyester or cotton thread in a weight that matches the original — if the shirt was sewn with heavy-duty thread, use the same. Test on a scrap first if you are unsure.

Do I need a serger to finish the seams?

No. A zigzag stitch on a regular machine works fine and prevents fraying. A serger creates a more polished finish and is faster, but it is not necessary for a shirt to hold up well. Pinking shears are another option if you do not have a zigzag stitch.

What if the shirt is too big everywhere?

Take in the side seams first, then assess what else needs adjusting. If the shoulders are also too wide, move those seams. If the sleeves are too long, shorten them. Doing one alteration at a time and trying the shirt on between each one prevents mistakes.

Can I undo an alteration if I change my mind?

If you have not trimmed the old seam away, yes — unpick your new seam and the shirt returns to its original size. Once you cut away the old seam allowance, you cannot undo it. This is why testing the fit before cutting is important.