Quick Answer
To add side panels to a shirt, open the side seams with a seam ripper, cut two wedge-shaped fabric panels using a simple paper pattern, then pin and sew each panel into the opening. This adds width exactly where a tight shirt needs it, and lets you add contrast fabric for a custom look. Most sewers finish this project in under an hour.
Key Takeaways
- Adding side panels can widen a shirt by 4–8 inches total, split evenly between both sides.
- For stretchy t-shirt fabric, use a ballpoint needle and a narrow zigzag or stretch stitch so the seam moves with the fabric.
- Always add a 1/2-inch seam allowance around your paper pattern before cutting fabric.
- Match the weight and stretch of your new fabric to the original shirt for the best drape and durability.
If you’ve got a favorite t-shirt sitting in the back of the closet because it’s just a little too snug, you don’t have to give it up. In my 15 years of altering and redesigning garments, adding side panels is one of the fastest fixes I recommend — it widens the shirt exactly where it’s tight and gives you a chance to add a contrast fabric for a completely custom look.
This guide walks through the entire process from opening the seams to sewing the final stitch, with the exact measurements and stitch settings I use in my own alterations.
Why Add Side Panels to a Shirt Instead of Buying a New One?
This simple alteration solves two problems at once.
First, it’s the most reliable way to make a shirt bigger without it looking altered. If a top pulls across the chest or feels tight at the waist, panels add room exactly where it’s needed instead of stretching the whole garment out of shape. Second, it’s a design opportunity. A plain black tee with floral side panels, or a white top with striped panels, turns a “too small” shirt into a piece you actually reach for.
What Do You Need to Add Side Panels to a Shirt?
You likely already have most of these tools in your sewing kit.
| Tool or Material | Why You Need It |
|---|---|
| The T-Shirt | The top you want to alter. |
| New Fabric | For the side panels. Match the weight and stretch percentage of your shirt as closely as possible. |
| Seam Ripper | To carefully open the side seams of your shirt. |
| Ruler or Tape Measure | For measuring the seam length and panel width. |
| Paper & Pen | To draw a simple pattern for your panels. Gift wrap paper works well. |
| Fabric Scissors | For a clean, precise cut. |
| Sewing Machine, Thread & Ballpoint Needle | A ballpoint needle prevents skipped stitches and small holes on knit fabric. |
| Pins or Sewing Clips | To hold the fabric together while you sew. |
How to Add Side Panels to a Shirt: Step-by-Step
Here’s the exact process I use, broken into five stages.
Step 1: Open Up the Side Seams
Lay your shirt flat and use a seam ripper to unpick the stitches along one side seam. The easiest method is to find the main needle thread and pull it out, rather than cutting every individual stitch.
Rip the seam all the way up to where the sleeve attaches at the armpit, and stop just below it — don’t cut into the armpit seam itself. Repeat on the other side so the shirt is open on both sides, ready for its new panels.
Step 2: Measure and Create Your Pattern
Try the shirt on, or measure around your waist, to figure out how much extra room you need. If you want 6 inches of total extra space, add a 3-inch wide panel to each side.
- Measure the Length: Measure the side seam you just opened, from the bottom hem up to the armpit — for example, 15 inches.
- Draw the Pattern: On paper, draw a long triangle (a wedge) with the point at the top. Make the length of the triangle match your side seam measurement.
- Set the Width: The bottom of the triangle equals the width you want to add to that side.
- Add Seam Allowance: Add a 1/2-inch of extra space around the entire pattern. Skipping this step is the most common reason the finished panel ends up too narrow.
Step 3: Cut Your Fabric Panels
Lay your new fabric flat, pin the paper pattern on top, and cut around it with fabric scissors. Cut a second, identical panel — you need one for each side of the shirt.
Step 4: Pin the Panels to Your Shirt
Lay your shirt open with the right side facing up. Place a fabric panel on top of one open side, right sides of the fabric together, and line up the long edge of the panel with the edge of the shirt opening.
Pin or clip from the bottom hem up to the armpit, matching the pointed top of the panel to the top of the seam. Bring the other side of the shirt opening over and pin it to the other edge of the panel, right sides together, so the panel is sandwiched inside the opening.
Step 5: Sew Your New Side Panels In
Do Side Panels Work on Stretchy T-Shirt Fabric?
Yes, side panels work well on stretchy t-shirt fabric as long as you use the right stitch. A narrow zigzag or a dedicated stretch stitch, set around 2.5mm long, lets the seam flex with the fabric instead of popping when you move. A ballpoint needle also prevents the small holes and skipped stitches that a standard needle causes on knits.
Start sewing near the top of the armpit, securing the front of the shirt to the panel, and sew down the entire length to the bottom hem. Then go back to the top and sew the other side, securing the back of the shirt to the other edge of the panel — pivoting carefully at the armpit corner for a clean point. Trim any loose threads, then repeat the pinning and sewing process for the second panel.
Common Mistakes When Adding Side Panels to a Shirt
These are the mistakes I see most often when sewers try this alteration for the first time.
- Skipping the seam allowance. Forgetting the 1/2-inch allowance around your paper pattern leaves the finished panel narrower than planned.
- Using the wrong needle on knit fabric. A standard sharp needle can pierce and break the knit’s fibers, causing tiny holes along the seam over time.
- Mismatching fabric weight. A heavy woven panel on a lightweight jersey tee will pull and distort the shirt’s drape.
- Sewing with a straight stitch on stretch fabric. A straight stitch has no give, so the seam will snap the first time you reach or stretch.
- Not stopping the seam rip below the armpit. Ripping too far into the underarm seam creates extra repair work before you can even start attaching the panel.
FAQs
How do you add side panels to a shirt?
Open the side seams of the shirt with a seam ripper, stopping just below the armpit. Cut two wedge-shaped fabric panels using a simple paper pattern with a 1/2-inch seam allowance. Pin each panel into an open side and sew it in place with a stretch or zigzag stitch.
How to put side slits in a top?
Decide how high you want the slit to sit, then use a seam ripper to open the side seam up to that point. Fold the raw fabric edges inward and press them with an iron. Sew a new, clean hem along the fold to finish the edge.
How to tighten the top of a shirt?
Add small folds called darts to the front or back to remove extra fabric and create shape. You can also re-sew the side seams narrower to pull the shirt in for a closer fit. Try the shirt on inside-out and pin the changes before sewing to check the fit first.
What are side slits on shirts called?
Side slits on a shirt are most commonly called “side slits” or “side vents.” Both terms describe the same feature: an opening left at the side seam of a garment. They’re common on longer tops and tunics to allow easier movement.
How to side slit a tshirt?
Use a seam ripper to open the side seam up to the length you want the slit to be. T-shirt knit fabric doesn’t fray much, so you can leave the raw edge as-is for a casual look. For a cleaner finish, fold the edge over once and sew a narrow hem.
Can you add side panels to any type of shirt?
Yes, side panels work on both knit t-shirts and woven button-up shirts, but the technique changes slightly. Knit fabric needs a stretch or zigzag stitch and a ballpoint needle, while woven fabric holds a standard straight stitch with a regular sharp needle.
How much bigger does adding side panels make a shirt?
A typical side panel alteration adds 4 to 8 inches of total width, split evenly between the two panels. You control the exact amount by setting the width of your paper pattern before cutting the fabric.
What fabric should you use for shirt side panels?
Choose a fabric that matches the weight and stretch percentage of your original shirt as closely as possible. For a stretchy cotton tee, look for a jersey knit with similar stretch. For a woven shirt, a cotton poplin or similar woven fabric will hold its shape correctly.
Do you need a special sewing machine to add side panels?
No, a standard home sewing machine with a zigzag stitch option is enough for this project. You’ll want a ballpoint needle on hand if you’re working with knit fabric, since it prevents skipped stitches and small holes.
You Did It! A Perfect-Fitting Custom Shirt
Turn your shirt right-side out and take a look — you’ve turned a too-tight tee into a shirt that fits and has a custom touch no one else’s has. In my own alterations, this is one of the fastest ways to rescue a shirt that would otherwise sit unworn.
Once you’re comfortable with this technique, you can apply it to tank tops, dresses, and even fitted jackets whenever you need a little extra room. What fabric will you use for your first pair of panels? Let us know in the comments below.