⚡ Quick Answer: How to Sew an Oversized Boxy T-Shirt
Sew an oversized boxy t-shirt by drafting a straight-sided body from four measurements: chest plus 12 to 15 cm of ease, shoulder width plus 5 to 8 cm of drop, body length to mid hip, and a neck opening about 20 cm wide. Cut a front and back on the fold, two sleeves, and a neckband at 85 to 90 per cent of the neck opening. Sew the shoulders, set the sleeves flat, close the side and sleeve seams in one pass, attach the band in the round, then hem the body and sleeves with a stretch stitch. Use a ballpoint needle, a narrow zigzag and a knit of at least 5 per cent stretch.
Most “boxy tee” tutorials are about cutting up a t-shirt you already own, which is a different job from sewing one. This guide drafts the shape from four measurements and sews it from flat pieces, so the result is the fit you chose rather than whatever the original shirt allowed.
The boxy silhouette is not a big t-shirt. It is a straight side seam, a drop shoulder and a wide neck, and each of those is a number you set on paper before you cut. Get the three numbers wrong and the shirt looks like a sack; get them right and it hangs the way the ones in the shops do.
What Makes a Boxy Tee Different
A fitted t-shirt follows the body: it is shaped at the waist, the sleeve cap curves to meet a set-in armhole, and the shoulder seam sits on the shoulder bone. A boxy tee does the opposite. The side seam runs straight from armpit to hem, the shoulder line drops past the shoulder bone, and the sleeve hangs from a nearly straight armhole instead of a curved one.
Sew knits with a ballpoint or jersey needle and a narrow zigzag, not a straight stitch. A straight stitch has no stretch in it, and the first time the shirt goes over your head the shoulder seam will pop.
That straightness is what makes the shirt easy to sew and hard to fit. There is no dart and no curve to hide a mistake in, so every number you pick is visible in the finished garment.
| Feature | Fitted tee | Boxy tee |
|---|---|---|
| Chest ease | 5 to 8 cm | 12 to 15 cm |
| Shoulder | On the shoulder bone | 5 to 8 cm past it |
| Armhole | Curved, set in | Nearly straight, 2 to 4 cm cap |
| Side seam | Shaped at the waist | Straight from armpit to hem |
| Neck opening | 17 cm | 20 to 22 cm |
The two numbers people get wrong are ease and drop. Ease less than 10 cm gives you a loose t-shirt that still looks fitted at the waist, and drop beyond 8 cm starts to bind under the arm when you lift it.
Step 1: Draft the Box From Four Measurements
Take the chest measurement around the fullest part, then add your ease. For an oversized boxy tee that is 12 to 15 cm, and the smaller figure is already loose. Divide the total by four and you have the width of the front piece at the chest, because each piece is a quarter of the body.
The length runs from the shoulder line to mid hip, which is 60 to 68 cm on most adults. Measure a shirt you already like from the shoulder seam straight down, and use that instead of a standard figure, because body length is the one dimension where a standard number looks wrong on a tall or short frame.
The drop shoulder is the number that decides whether the shirt reads as boxy or as simply too big. Measure your shoulder width across the back from bone to bone, add 5 to 8 cm, and divide by two for the half width on each piece. Add less and the sleeve sits on the shoulder like a normal tee; add more and the seam lands halfway down the upper arm, which is where the oversized look actually comes from.
| Number | How to get it | Boxy tee figure |
|---|---|---|
| Body width | (Chest + ease) divided by 4 | 28 to 32 cm |
| Body length | Shoulder to mid hip | 60 to 68 cm |
| Shoulder drop | Shoulder width plus 5 to 8 cm, halved | 24 to 27 cm |
| Neck width | Straight across the front neck | 20 to 22 cm |
Draw the front with a straight side seam from the hem to the armpit, a horizontal line at the shoulder, and a gentle curve only at the neck. The back is the same piece with a neck curve 2 cm higher at the centre and no other change. Add 1 cm seam allowance everywhere and 3 cm at the hem.
Step 2: Choose Knit, Needle and Stitch
Cut the neckband shorter than the neck opening, not longer. A band cut to the same length as the opening has nowhere to go, and that is the pucker everyone blames on the machine.
Any knit with at least 5 per cent stretch sews into a boxy tee, but the weight changes the look more than the fibre does. A light jersey at 150 gsm drapes and clings; a heavy cotton jersey at 220 gsm holds the boxy shape and is the weight most shop-bought oversized tees use. A French terry at 260 gsm is a sweatshirt, whatever the pattern says.
| Knit | Weight | What it does in a boxy tee |
|---|---|---|
| Cotton jersey | 150 gsm | Drapes, clings at the hip, needs a heavier body |
| Cotton jersey, heavy | 210 to 230 gsm | Holds the box, the standard choice |
| Rib knit | 240 gsm | Holds the shape, narrow width, needs piecing |
| French terry | 260 gsm | Sweatshirt territory, drop the ease to 8 cm |
| Viscose blend | 170 gsm | Drapes beautifully, grows with wear |
Use a ballpoint or jersey needle in 75/11 for jersey and 80/12 for heavier knits, and change it every two garments because knits blunt a needle faster than wovens do. Set the machine to a narrow zigzag, 0.5 mm wide and 2.5 mm long, or an overlock stitch if the machine has one. Straight stitch has no stretch and will crack at the shoulder the first time the shirt is pulled on.
Thread matters less than people think, but it has to be all-purpose polyester, not cotton, because cotton thread has no give either. A walking foot helps on viscose blends that slide, and a strip of tear-away stabiliser under the shoulder seam stops the fabric being pulled down into the plate.
Step 3: Cut the Body and the Sleeves
Fold the fabric with the selvedges together and the right side inside, lay the front piece on the fold, and cut. The fold becomes the centre front, which means no seam down the middle and no chance of the two halves being different shapes.
Cut the back on the fold as well, with the neck 2 cm higher at the centre. Then cut the two sleeves as mirror images, which matters more than it sounds: a boxy tee has a shallow sleeve cap of only 2 to 4 cm, and two sleeves cut the same way round leave one with the cap on the wrong edge.
Mark the shoulder points and the armpit notches with a snip no deeper than 5 mm. On a straight-seamed tee the notches are the only thing that keeps the front and back matched, because there is no curve to feel your way along.
Cut the neckband from rib knit, or from the same jersey if there is no rib, at 85 to 90 per cent of the neck opening and 4 cm wide. Cut it so the greatest stretch runs along the length of the band, not across it, which is the difference between a band that recovers and one that stays stretched out.
Step 4: Shoulders First, Then Sleeves Flat
Sew the front to the back at both shoulders with the right sides together, then press the seam allowances towards the back. Add a strip of clear elastic or a second row of stitching in the seam allowance if the shirt is heavy, because a shoulder seam carries the whole weight of the garment and knits stretch there.
Set the sleeves while the body is still open and flat. Match the sleeve notch to the shoulder point, pin the sleeve cap to the armhole with the sleeve underneath, and sew. A shallow cap has almost no ease to distribute, so it goes in without pinning in most cases, and the flat method removes the risk of a pucker at the underarm that takes twenty minutes to unpick.
Press the seam allowance towards the body, not towards the sleeve, which keeps the sleeve hanging cleanly instead of standing up at the shoulder.
Step 5: Close the Side and Sleeve Seams in One Pass
Fold the shirt right sides together with the front and back matched at the armpit, then sew from the sleeve cuff all the way to the hem in a single pass. One seam, no interruption, and the armpit intersection is where the two curves meet at right angles.
Match the underarm seam of the sleeve to the side seam of the body before you start, and pin from there outwards in both directions. The armpit point is the only place that has to be exact; everything else can be eased as you sew.
Use a stretch stitch or an overlock, and if the machine has a differential feed, set it at 1.2 to stop the seam waving. Jersey that has been stretched as it sewed will show a ripple along the whole side seam, and pressing will not remove it.
If the fabric curls badly at the hem, staystitch 1 cm from the edge before you sew the side seam, or fuse a strip of knit interfacing into the hem allowance. Either one holds the hem flat long enough to be turned and stitched.
Step 6: The Neckband That Does Not Pucker
Sew the short ends of the band together to make a loop, press it flat folded in half with the right side out, and mark it into quarters. Mark the neck opening into quarters too, at the centre front, the centre back and both shoulders.
Pin the band to the opening right sides together, matching quarter to quarter, then pin halfway between each pair. Stretch the band to fit as you sew, not the opening. The band is shorter than the opening on purpose, and the stretch is what makes it lie flat.
Sew with a narrow zigzag at 6 mm from the raw edge, then trim the allowance to 6 mm and press the band up. Topstitch from the right side if the machine handles knits well, and skip it if it does not, because a wobbly topstitch on a neckline is more visible than no topstitch at all.
If the first attempt puckers, the band was cut too long or stretched while it was sewn. Both are recoverable: unpick, re-cut the band 2 per cent shorter, and sew it again without pulling it through the machine.
Step 7: Hem the Body and the Sleeves Last
Press the hem allowance up by 2.5 cm, then stitch it with a twin needle from the right side. A twin needle gives two parallel lines of stitching on the front and a zigzag on the back, which is exactly how shop-bought tees are finished and the reason their hems stretch.
If there is no twin needle, a narrow zigzag 3 cm from the edge, or a stretch stitch, both work. What does not work is a straight stitch, which snaps the first time the hem is pulled over the hips.
Hang the shirt for an hour before hemming if the fabric is a viscose blend, because those knits grow under their own weight and a hem cut level will be uneven by the time the garment settles. Then check the hem against the floor and trim before stitching.
Sleeve hems take the same treatment at 2 cm, and on a boxy tee they are usually left wide rather than tapered, because a tapered sleeve fights the straight side seam and pulls the whole shape in.
Fixing a Boxy Tee That Went Wrong
| What you see | What caused it | The fix |
|---|---|---|
| Sleeve binds when you lift your arm | Too much shoulder drop | Reduce the drop by 2 cm, or add 1 cm to the armhole depth |
| Shirt looks like a sack | Ease over 18 cm, or a light fabric | Cut 3 cm from each side seam, or use a heavier jersey |
| Side seam waves | Fabric stretched while sewing | Sew again with differential feed at 1.2, do not pull |
| Neckline ripples | Band cut too long, or stretched | Re-cut the band 2 to 3 cm shorter and resew |
| Shoulder seam pops | Straight stitch used | Resew with a narrow zigzag and add clear elastic |
| Hem curls up | Allowance too narrow | Re-hem with 2.5 cm and a twin needle |
Six faults, and five of them are fixed without recutting anything. The one that needs fabric is the ease, so cut the first shirt 2 cm wider than you think and take it in after trying it on.
Frequently Asked Questions
How much fabric do I need for an oversized boxy t-shirt?
About 1.5 metres of 150 cm wide knit for one shirt up to a 110 cm chest, and 1.2 metres if the fabric is 180 cm wide. Add 30 cm if you want the sleeves long, because a long sleeve on a dropped shoulder takes more length than a set-in one.
What fabric is best for a boxy t-shirt?
A heavy cotton jersey at 210 to 230 gsm holds the boxy shape and is what most shop-bought oversized tees use. Lighter jersey at 150 gsm drapes and clings at the hip, and viscose blends grow with wear, so the shirt gets longer and looser as the day goes on.
How do I draft a boxy t-shirt without a pattern?
Draw a rectangle as wide as a quarter of your chest plus 12 to 15 cm of ease, and as long as the shoulder-to-hip length you want. Make the side seam straight, drop the shoulder 5 to 8 cm past your shoulder bone, add a shallow 2 to 4 cm sleeve cap, and cut a neck opening about 20 cm wide.
Why does my t-shirt sleeve pull when I lift my arm?
Almost always too much shoulder drop combined with a shallow armhole. Reduce the drop by 2 cm, or add 1 cm to the depth of the armhole so the sleeve has room to rotate. A boxy tee should hang from the shoulder rather than grip the upper arm.
How wide should a t-shirt neckband be cut?
Cut the band at 85 to 90 per cent of the neck opening for a standard jersey, or 80 per cent for a rib knit, and 4 cm wide. The band is deliberately shorter than the opening, and the stretch is what makes it lie flat instead of waving.
Can I sew a boxy t-shirt on a regular sewing machine?
Yes, with a narrow zigzag set to 0.5 mm wide and 2.5 mm long, and a ballpoint needle. A serger finishes the seams more neatly but is not required. What is required is a stitch with stretch in it, because a straight stitch cracks at the shoulder the first time the shirt goes over your head.
What is the difference between an oversized t-shirt and a boxy t-shirt?
An oversized tee is a normal shape cut larger, so it gets bigger everywhere including the shoulder. A boxy tee keeps the shoulder dropped and the side seam straight on purpose, which changes the silhouette rather than just the size.
How do I stop the hem curling on a knit t-shirt?
Use a 2.5 cm hem allowance, press it up before stitching, and finish it with a twin needle or a narrow zigzag. A narrow allowance curls because there is not enough weight in the fold, and a straight stitch adds curl by pulling the fabric as it sews.
Should I wash the fabric before sewing a t-shirt?
Yes. Pre-wash and dry the knit the way you will wash the finished shirt, because cotton jersey can shrink 5 per cent or more on the first wash, and a boxy tee that shrinks after cutting becomes a fitted tee with a short body.
Why does my neckline look wavy after sewing?
The band was either cut too long, so it had nothing to gather, or it was stretched while it was sewn. Re-cut the band 2 to 3 cm shorter than the opening, quarter both the band and the opening, and stretch the band rather than the shirt as you sew.
Conclusion
A boxy tee is four measurements, three straight seams and a band, and it sews in an afternoon once the draft is right. Set the ease at 12 to 15 cm, drop the shoulder by 5 to 8 cm, keep the side seam straight, and cut the neckband short so it has somewhere to go.
The questions readers ask most, including whether an oversized tee is the same garment as a boxy one, are answered in the FAQ at the end of this page. The common mistakes are all one of three: treating it as a big t-shirt when it is a different shape, cutting the neckband the same length as the opening so it has nothing to gather, and sewing the shoulders with a straight stitch that cannot stretch. It is a different shape, and the drop shoulder is what makes it read as deliberate rather than as a size too large.
If you want to go further with the same block, drafting a puffy sleeve uses the same body and changes the sleeve, and the basics of using a sewing machine cover the stitch settings that knits need.
Tell us which number you used for the drop, because that is the one most readers get wrong and the one that decides the whole shape. Did yours come out boxy, or just big?
About This Guide
This guide was written from the standard drafting method for a boxy knit block and checked against the ease and drop figures published by independent pattern makers for oversized tees. The fabric weights are the ones the mills quote for the jerseys most often sold as t-shirt knits.
Mithu has sewn knit tees for 15 years and keeps a shirt on the wall of her workroom with a shoulder seam that was sewn with a straight stitch, because it split the first time it was worn and it is the reason every knit guide she writes starts with the needle and the stitch.
All images in this article were created using AI.