How to sew a comfortable t-shirt with a gusset

A gusset can transform the fit and movement of a handmade t-shirt. This small fabric insert, usually placed beneath the arm, gives extra room through the underarm without making the whole garment oversized. It is especially useful for activewear, relaxed tops, and knit garments that need to move comfortably.

Sewing a T-shirt with a gusset may look more complicated than making a standard tee, but the process becomes manageable once the pieces are marked clearly and sewn in the right order. The key is to work methodically, match the stretch direction, and avoid pulling the fabric as it passes beneath the presser foot.

This guide focuses on practical construction, from choosing suitable jersey to finishing the neckline and checking the fit. The same principles can be applied to a Love Notions pattern, another independent sewing pattern, or a self-drafted knit top.

Why add a gusset?

A gusset is an extra piece of fabric inserted into a seam to improve comfort, strength, or range of movement. In a t-shirt, it is commonly shaped like a diamond, rounded triangle, or narrow panel and positioned at the underarm. When the arm lifts, the gusset spreads the strain across several seams rather than concentrating it at one point.

This detail is useful when a regular sleeve feels restrictive, particularly on close-fitting garments. It can also help if you are adapting a pattern for cycling, yoga, gardening, or everyday movement. A gusset will not correct every fitting problem, though. If the bodice is too narrow across the bust or the sleeve is too tight at the bicep, those areas still need adjusting.

The insert can be made from the same jersey as the rest of the tee for a quiet finish, or from a contrast fabric for a visible design feature. A stable contrast knit may be easier to handle than a very fluid main fabric.

Choose fabric and prepare your tools

Medium-weight cotton jersey with around 30–50 percent stretch is a friendly starting point. Cotton-spandex, bamboo jersey, and many modern performance knits can work well too. Check the pattern recommendations before cutting, since a gusset relies on the fabric stretching and recovering consistently with the surrounding pieces.

Avoid pairing a very firm jersey with a loose, drapey knit. The different behaviour can cause rippling at the seams. Wash and dry your fabric in the same way you plan to launder the finished garment, then allow it to rest before cutting. This prevents a first-wash surprise from changing the fit.

Use a ballpoint or stretch needle, polyester thread, and a narrow zigzag or stretch stitch. An overlocker is convenient but not essential. A regular sewing machine can produce a durable result with a zigzag, lightning stitch, or a narrow seam finished with pinking shears if the fabric does not fray.

A walking foot can help feed the layers evenly, especially around the curved underarm. Keep fabric scissors, clips, a fabric marker, a ruler, and a small pressing cloth nearby. Clips are often preferable to pins because they do not create runs in delicate jersey.

Mark every gusset piece carefully

Before cutting, read the pattern instructions from beginning to end. Check whether the gusset is included as a separate pattern piece or whether you need to draft it from the underarm opening. Note the grainline, stretch direction, seam allowance, and any notches. A gusset that is rotated incorrectly may fit at the start but restrict movement once the top is worn.

Transfer all notches to the fabric. Mark the front and back of the gusset if the shapes are similar, and label each piece with a removable marker or a small paper tag. The underarm can become confusing when the garment is partly assembled, so clear labels save time.

If you are drafting your own insert, make a paper template first. Hold the front and back bodice pieces together at the side and sleeve seams, then measure the opening you want to fill. Draw a symmetrical diamond or a slightly curved panel, adding the required seam allowance around every edge. Use scrap fabric to test the shape before cutting into your chosen jersey.

Follow a steady sewing order

The order of construction makes the greatest difference to the final result. First sew the shoulder seams, unless your pattern uses a different assembly method. Stay-stitch or reinforce them if the knit has a tendency to stretch. Attach the neckband while the garment is still relatively flat, or follow the pattern’s recommended sequence.

Next, join the gusset to one side of the underarm opening. Match the central notch first, then clip or pin towards each corner. Sew slowly, using a stretch stitch and a consistent seam allowance. Do not stretch the gusset into place unless the instructions specifically require it; the edges should meet naturally.

Once the first seam is secure, attach the corresponding sleeve or bodice edge to the remaining gusset sides. Press the seams gently towards the sleeve or open them if the fabric is bulky. A small scrap of jersey placed between the iron and the garment can prevent shine or distortion.

Stage	What to check	Helpful technique
Prepare	Grainline, stretch, notches, and labels	Compare both gusset pieces before sewing
Attach first edge	Centre points and seam allowance	Clip around curves and sew slowly
Join remaining edges	No twisting or trapped fabric	Keep the garment right sides together
Secure seams	Even stitching and comfortable bulk	Use a stretch stitch and light pressing
Complete side seams	Underarm points align	Match seams before sewing towards the hem
Test movement	Arm lifts without strain	Try the tee on before final topstitching

After the gusset is attached, sew the side seams and sleeve seams as directed by the pattern. Some designs are sewn in one long seam from cuff to hem, while others are assembled separately. Match the underarm junction carefully, since even a small mismatch can create a lump or pull line.

A short length of straight stitching at the very end of a seam can lock the thread, but avoid backstitching heavily on lightweight jersey. A few reverse stitches or thread tails tied securely by hand are usually enough.

Refine the fit and finish

Try the t-shirt on before hemming. Raise both arms, reach forward, and rotate your shoulders. The gusset should lie flat without digging into the underarm. Look for drag lines radiating from the insert. A little movement in the fabric is expected, but strong horizontal or diagonal pulls may indicate that the gusset is too small or that the sleeve needs more width.

If the underarm feels comfortable but the bodice rides up, check the overall length and hem circumference. If the sleeve hangs strangely, inspect the front and back notches and confirm that the gusset has not been sewn upside down. Unpicking one seam at this stage is much easier than correcting a finished hem.

For the neckline, a twin needle, coverstitch, or narrow zigzag can create a flexible finish. Stabilise the shoulder seams with clear elastic or a strip of lightweight knit interfacing if they stretch during construction. Press the neckband away from the garment and use a few careful stitches in the seam allowance to keep it rolled inward.

Finish the sleeve and hem edges with a twin needle or a stretch stitch. Let the machine feed the fabric; pulling it while sewing can create a wavy hem that may not relax after washing. A light steam press, followed by cooling the garment flat, often helps the stitches settle.

Keep these checks beside the machine

The gusset is a small detail, but accuracy matters because several seams meet in one compact area. Take a moment to inspect the fabric after every seam, especially if you are using a slippery rayon jersey or a very stretchy athletic knit.

These practical checks will make the process calmer and reduce avoidable unpicking:

• Test your needle, stitch length, and thread tension on a fabric scrap first.
• Use clips and plenty of notches so the gusset cannot be accidentally twisted.
• Sew with the gusset against the feed dogs when possible to help ease in a curved edge.
• Check arm movement before adding the final sleeve and hem finishes.
• Wash the completed tee before judging the long-term fit or fabric recovery.

Keep notes about the pattern size, fabric stretch, gusset dimensions, and any alterations. Those details are valuable when you make a second version, particularly if the first top reveals that you prefer a deeper underarm or a wider sleeve.

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Make the design your own

Once the construction feels familiar, the gusset becomes an opportunity for creativity rather than an intimidating extra step. Try a striped insert, a breathable mesh panel, or a small piece of leftover jersey from another project. Keep the stretch direction consistent, and make sure the contrast fabric is comfortable against the skin.

You can also adapt the shape for a closer or roomier fit. A longer diamond can provide more movement, while a shallow curved insert may look subtler. Make each change first on a paper or scrap-fabric version, then transfer the successful adjustment to your pattern.

A well-made gusseted t-shirt should feel easy to wear, easy to move in, and strong enough for regular washing. Choose a fabric you enjoy handling, mark the pieces clearly, and take your time at the underarm junction. Then sew a test version, wear it through an ordinary day, and use what you learn to create the next one with confidence.