Plenty of people have written about the (really quite big) issues involved in providing various sizes of promotional t-shirts. Very brief recap: the “unisex” sizes of t-shirts are usually cut for taller and straighter bodies, and tend to look less great on shorter, rounder, or curvier bodies. Quite a few vendors of curvier-cut blank shirts use measurements that are -unusually- small – so even if curvier cuts are offered, they fit fewer people. (Some of the same vendors that use extremely small measurements for curvy shirts also use smaller and tighter measurements for angular-cut shirts – using these companies may result in short-changing -all- of your larger conference attendees. If you’re allowing people to pre-order shirts, including the brand name for the blank shirts can be very helpful to let people check measurements.)

TL;DR – if you like curvier-cut t-shirts, and especially if you are on the larger side, you will often find nothing that fits you in a range of promotional t-shirts. But if you have a sewing machine, you can fix that.

First, take a shirt whose fit you -do- like, and trace it. (If you don’t have a roll of tracing paper, cut open a paper grocery bag for a big surface to trace.) My favorite curvy-cut shirt is Anvil brand, size XL. (I also like Gildan.)

Close view of the collar of a grey t-shirt. A hand is holding down the tag to show the brand name "Anvil" and size XL

You’ll want to trace the front and back (shirt patterns usually use a half-width shape: fold the shirt, shoulders together, to trace a half-pattern of the front side; then reverse to trace the back.) Trace around the folded shirt: the curve of the neck hole, the top shoulder seam, side seam, and bottom hem are pretty easy. The seams where the sleeves are attached are a little harder to trace; I fold the sleeve up a bit and feel where the seam goes with my fingers, tracing a dotted line underneath the fabric.

Grey t-shirt lying on a white piece of tracing paper (which is itself lying on a green cutting mat.) The top shoulder seam and side seam of the shirt have been traced on the paper, and a hand is pulling back the sleeve to show how to trace the edge of the arm hole.

Then I pick up the shirt and connect the dotted line. Do the same to trace the sleeves. A surprising fact: the front and back of the sleeve seams are -not- the same. It’s possible to use a single symmetric curve on front and back, but the different lines do look a little bit better. (The technical word for the line around the sleeve-hole is “armscye”.) Eventually you’ll have four pattern pieces traced: half-front, half-back, and front and back of sleeves.

A large piece of tracing paper lying on the floor, on a green cutting mat. The outlines of the front and back halves of a t-shirt, and the front and back of the sleeves, have been traced onto the paper.

When picking a shirt to re-cut, you may need a size up from what you normally settle for in a straight/angular-cut shirt. The most important dimension (for me) is to make sure there’s enough width around my hips. I happily wear an XL (or sometimes even L) in straight shirts, but usually find I need to start with a 2XL for the most comfortable cut-down shirts.

Might be a good idea, the first time you try this, to try cutting down a shirt you don’t mind messing up? Thrift stores are a good source for this. I’ve done this a few times now, so the process below takes me maybe an hour or so, if I don’t try to do it when I’m too tired to do floppy geometry correctly in my head. (Sleepy sewing = mistakes.)

First step is, cut off the sleeves! (You’re going to be narrowing the shoulders -and- shortening the sleeves, so it doesn’t really matter much which side of the seam you cut on.) Fold the sleeveless shirt in half as you did when tracing the pattern, and lay the relevant pattern piece on top.

A dark navy t-shirt with its sleeves cut off, has been folded in half with the front of the shirt facing out. A sewing pattern piece for the front of a t-shirt is lying on top of the shirt - it's one of the pieces obtained by tracing in the previous step.

Trace around the pattern piece (I used tailors chalk, but regular chalk works, too. Or on a light shirt, a disappearing-ink fabric pen.) Note that it -won’t- all line up quite right. Since the arm holes on the curvy-cut shirt are usually a little smaller, the armpit in particular won’t line up quite where you expect. It’s okay, just trace approximately – knits are pretty forgiving.

Dark navy t-shirt with the sleeves cut off, folded in half and lying on the floor, with chalk lines drawn on it to outline the pattern piece from the previous step.

Trim off the hem (leave extra space below the line you traced, as a seam allowance.) Trim off the sleeve hole, also leaving extra fabric outside the line – although it’s okay to get pretty close to the line at the very top of the shoulder seam – the head hole on angular-cut shirts is usually a little bigger than than of the curvy-cut shirts, so you can bring in the shoulders a little more than the specific lines you traced.

DO NOT CUT ANYTHING OFF AT THE SIDE SEAM, except to cut open the side seam for few inches below the armpit. Don’t cut all the way down to your hem, or even down to where your chalk line hits the side seam.

Trace the front and back of the sleeve pattern pieces onto the sleeves you cut off. Label the front and back. Make sure you have a left sleeve and a right sleeve. (I.e., if you have both front sides up, the sleeve hems should point in different directions.) The pictures below are of the front and back of the same sleeve.

Turn the main body of the shirt inside-out, and insert the sleeve in the appropriate hole (i.e., lining things up so the front of the sleeve will be attached to the front of the shirt.) Note that the hem of the sleeve should be -inside- the body of the shirt while you do this; you’re sewing the seam inside-out.

Note! When sewing knits, use a double needle or a zig-zag stitch, or all your seams will tear the first time you wear the shirt! A fairly small zig-zag width gives you a decent amount of stretch. That’s what I’ve used below.

Pin the sleeve to the shirt. Since you didn’t cut any fabric away from the sleeve, there will be some sticking out of the hole. But try to roughly line up the edge you cut on the main body of the shirt with the line you traced on the sleeve. (Again, knits are forgiving. You could use a smooth curve here and it’d probably look okay in the end.) Sew around the sleeve from armpit to armpit. (When you’re done, there will be a little hole in the armpit where you cut a few inches along the side seam. That’s okay, you want that!)

Navy t-shirt fabric next to a sewing machine. Two layers of fabric are pinned together, ready for sewing.
Remember, this is the inside-out shirt, with the sleeve inserted (hem-first) inserted into the armhole. I still have to turn things and get the free arm on my sewing machine inside the armhole to sew the sleeve on.

Now comes the step where you have to improvise the most. You’re going to angle the side seam to make the shirt curvier, but remember that the armpit was kind of wacky when the pattern piece was lying on top of the shirt before we started cutting? You’re going to kind of fake your way to a new armpit. 🙂

I actually laid the shirt out and traced the side seam from the pattern piece again, on the inside of the shirt. Then I sewed a more-or-less straight line from where the pattern hit my actual side seam, up to the armpit. The line I sewed does -not- quite match what I traced from the pattern piece. There’s a little flappy corner that sticks out to the side below the armpit – that’s from the previous armhole. (Note the bottom of the shirt is toward the -top- of the image below.)

closer view of previous image, with red arrow and the word "armpit" in red highlighting the armpit.

Fold the hem up to the line you traced (the fabric you left for seam allowance should go towards the inside of the shirt.) Secret tip: I often extend the back hem down just a little bit (maybe 2 cm longer in the center back, easing back up to the original line I traced at the sides) to give a little better back coverage. Sew around your new hem. You’re done!

Two navy blue t-shirts lying on the floor, spread out flat. Each has the DuckDuckGo search engine logo on the front (a cartoon duck in a green bow tie on a dark orange circle.) The shirt on the left has straight sides and a long hem. The shirt on the right has shorter sleeves, a shorter hem, and tapered sides.

(DuckDuckGo is a search engine that doesn’t track your activity as much as most others. It’s my primary search engine (I even re-set my browsers to use it as the default search) and I really like it. They didn’t give me any money to write this or anything, but one of their legal team members did send me some swag shirts a while back that I decided to use for illustration!)

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