How To · Fashion · Finish
The Right Way to Take In Side Seams
Taking in side seams is one of the most forgiving alterations you can master—and it transforms an ill-fitting garment into something that actually flatters your frame. Here's exactly how to do it without second-guessing yourself.
5 min read · IrisSide seams are the backbone of fit. When a shirt, dress, or jacket pulls across your ribs or hangs too loose, the solution almost always lives along those vertical lines running from armpit to hip. The good news: adjusting them requires only basic sewing skills and a steady hand.
This guide walks you through the entire process, from trying on the garment to finishing your stitches. You'll need a needle, thread, pins, and scissors—nothing more. The key is measuring twice and sewing once, because unpicking stitches is tedious.
The difference between a garment that fits and one that doesn't often comes down to a quarter-inch adjustment on each side seam.
What you'll need.
- 01Needle (size 8 or 9 for most fabrics)
- 02Thread (matching the garment color)
- 03Pins
- 04Scissors
- 05Measuring tape
- 06Tailor's chalk or fabric pencil
- 07Ruler (optional but helpful)
Step one · 1 minute
Try on the garment inside-out
Put on the piece and have someone pin the side seams to your actual body shape while you stand naturally. If you're alone, use a mirror and pin as you go. The pins should follow your body's contour—not the original seam line. This is your new seam placement. Mark both sides evenly to maintain balance.
Wear the undergarments and layers you'd normally pair with this piece. Fit changes dramatically depending on what's underneath.
Step two · 2 minutes
Measure the adjustment on both sides
Take off the garment carefully, keeping pins in place. Measure the distance between the original seam line and your new pin line at the bust, waist, and hip. Write down each measurement. The adjustment should be consistent—usually between a quarter-inch and one inch per side. If the measurements vary wildly, re-pin until they're even.
Uneven adjustments create a twisted, uncomfortable fit. Consistency matters more than perfection.
Step three · 1 minute
Draw a new seam line with tailor's chalk
Using your measurements, draw a straight line from armpit to hem on both side seams with tailor's chalk or a fabric pencil. Follow the pins as your guide, but make the line smooth and continuous. This becomes your stitching line. Double-check that both sides match—hold the garment up to a mirror or fold it in half to compare.
A ruler or straightedge helps create clean lines, especially if you're nervous about freehand drawing.
Step four · 3 minutes
Stitch along the new seam line
Thread your needle and tie a knot at the end. Starting at the armpit, use a backstitch (the strongest hand-sewing stitch) to follow your chalk line. Keep stitches small and even—about one-eighth inch apart. Sew slowly and deliberately. When you reach the hem, tie off with a secure knot. Repeat on the other side. If you have access to a sewing machine, this step takes 30 seconds, but hand-sewing is absolutely viable.
Backstitch by pushing the needle forward, then bringing it back through the previous stitch hole. It looks like a solid line and won't unravel.
Step five · 2 minutes
Try on and assess the fit
Put the garment on right-side out and check how it feels. Move your arms, sit down, bend forward—the seam should follow your body without pulling or bunching. If the fit is close but not perfect, you can make minor adjustments now by taking in or letting out a few stitches. If it's significantly off, you may need to re-sew.
Don't trim the excess seam allowance yet. Leave it intact until you're 100% confident in the fit.
Step six · 1 minute
Trim and finish the seam allowance
Once you're satisfied, trim the excess fabric from the original seam to about one-quarter inch from your new stitching line. This reduces bulk and prevents the seam from showing through on the outside. If the fabric frays easily, you can whip-stitch the raw edges or use pinking shears. For most garments, a simple trim is enough.
Save the trimmed scraps. They're useful for testing thread color or practicing stitches on similar fabric.
How to know it works.
A successful side seam alteration should feel invisible. The garment hugs your body without restricting movement, and the seam line sits directly on your side—not wrapping around to the front or back. You should forget the alteration exists within five minutes of wearing it.
Questions at the mirror.
What if I took in too much and now the armhole is too tight?
Carefully unpick your stitches and re-sew using a slightly shallower seam line. Even a quarter-inch difference at the armpit makes a noticeable change. This is why trying on before committing to stitches matters.
Can I take in side seams on stretch fabrics like jersey or spandex?
Yes, but use a ballpoint needle and stretch thread if possible. Hand-sewing stretch fabric is tricky because the thread can break under tension. A sewing machine with a stretch stitch is ideal, but a careful backstitch works in a pinch.
My stitches look uneven. Does it matter?
Uneven stitches on the inside are cosmetic only—no one sees them. What matters is that they're secure and follow a straight line. If they're truly chaotic, unpick and try again, but minor imperfection is fine.
Should I take in both side seams equally?
Almost always yes. Taking in different amounts on each side creates an asymmetrical, twisted fit. Measure carefully and aim for identical adjustments on both sides.