Front piece
The front controls chest width, front neckline depth, hem width, and the front half of each armhole.
Pattern pieces explained
T-shirt pattern pieces explained
A generated T-shirt pattern is not one shape. It is a set of pieces that sew together: body, sleeve, neckline finish, grain direction, and allowances.
A T-shirt looks like the simplest garment in the wardrobe, but the pattern behind it is still a small system: a front and a back that share shoulder and side seams, a sleeve whose cap must match the armhole it drops into, and a neckband that is deliberately shorter than the neckline it finishes. Each piece only makes sense in relation to its neighbours — change one edge and the piece next to it has to answer.
The generator drafts all four pieces from the same set of body measurements, so the seams that meet are drafted to meet: the front and back shoulder lengths agree, the sleeve cap is checked against the combined front and back armhole, and the neckband is calculated as a fraction of the finished neckline rather than guessed. On every piece you get a solid stitch line, a dashed cutting line with your chosen allowances already added, plus notches, fold marks, and a grainline.
This guide covers what the card list above does not: the order in which the pieces go together, how many of each to cut and from what, the construction mistakes that ruin knit tops, and which seams to adjust when you try the shirt on. Knit construction rewards a specific sequence — most of the classic T-shirt problems come from sewing the right seams in the wrong order.
Back piece
The back usually has a shallower neckline and must match the front at shoulder, side seam, and hem level.
Sleeve piece
The sleeve includes a cap curve that sews into the armhole and a lower edge that may be hemmed or finished with a cuff.
Neckband
The neckband is sewn around the neckline. For knit fabric it is usually slightly shorter than the neckline so it lies flat.
Grainline and stretch direction
The grainline helps place the piece on fabric. For knits, stretch direction must also be checked before cutting.
Seam and hem allowance
Dashed cutting lines include allowance. Hems may need more depth than regular seams.
How to use these pieces
Before sewing, check that shoulder seams match, sleeve cap fits the armhole, the neckband suits the fabric stretch, and the hem and seam allowances match your construction method.
Construction order
How the T-shirt pieces go together
Knit tops are traditionally assembled flat for as long as possible — the neckband and sleeves are far easier to handle before the garment becomes a tube. Use a stretch stitch, a narrow zigzag, or an overlocker throughout, and let the feed dogs move the fabric instead of pulling it.
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01
Join the shoulder seams
Place the front and back right sides together and sew both shoulder seams on the solid stitch line. On knits, stabilise these seams with clear elastic or a strip of fusible stay tape caught in the seam — shoulders carry the whole weight of the shirt and stretch out first. Press the seams toward the back.
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02
Prepare and attach the neckband
Fold the neckband in half lengthwise, wrong sides together, and join its short ends into a loop. The band is drafted at roughly 80–85% of the neckline length, so it must be stretched evenly as you sew: quarter both the band and the neckline with pins, match the quarter points, and stretch only the band between them. Sew with the band on top so you can control the stretch.
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03
Press the neckline before moving on
Press the seam allowance down toward the body and steam the band into a flat circle while the garment is still easy to lay flat. A neckband that ripples now will not improve later — if it stands away from the body, unpick and re-sew it with more stretch before assembling anything else.
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04
Set the sleeves in flat
With the side seams still open, match each sleeve cap to its armhole: centre notch to shoulder seam, and the single and double notches to the front and back armhole marks. A knit sleeve cap is drafted almost flat, so it eases in without gathers — the generator has already verified that cap and armhole lengths agree. Sew with the sleeve underneath and the body on top.
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05
Close the side and sleeve seams in one pass
Fold the shirt right sides together and sew from the sleeve hem, through the underarm point, down to the bottom hem in a single continuous seam on each side. Match the armhole seams exactly at the underarm — a pin placed through both seam lines keeps them aligned as they pass under the needle.
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06
Hem the sleeves and the bottom edge
Turn the hem allowances up along the fold marks printed on the pieces, press, and sew with a twin needle, a zigzag, or a coverstitch — anything that stretches. Let the shirt hang for a few hours before hemming if the knit is heavy or very stretchy, so the hem does not drop unevenly after the first wear.
T-shirt cutting plan
What to cut from the generated PDF and where each piece ends up. Lay all pieces with the grainline parallel to the selvedge and the greatest fabric stretch running around the body, not up and down it.
| Piece | Cut count | Fabric | Joins to |
|---|---|---|---|
| Front | Cut 1 on fold | Main knit | Back at shoulders and sides; sleeve at front armhole; neckband |
| Back | Cut 1 on fold | Main knit | Front at shoulders and sides; sleeve at back armhole; neckband |
| Sleeve | Cut 2 mirrored | Main knit | Armhole at the cap; body at the underarm seam |
| Neckband | Cut 1, stretch along length | Main knit or ribbing | Neckline, stretched evenly between quarter marks |
The dashed cutting line already includes your seam and hem allowances — cut on the dashed line and sew on the solid one. Before cutting anything, print at 100% and measure the 5 × 5 cm test square on the first sheet.
Common construction mistakes
Stretching the neckline while sewing
If the neckline edge is pulled as it goes under the needle, it grows permanently and the neckband can never pull it back flat. Staystitch or handle the raw neckline as little as possible, and stretch only the band — never the body — when attaching it.
Cutting the neckband the same length as the neckline
A band cut one-to-one gapes and flips outward. The generated band is deliberately shorter — around 80–85% of the neckline — so that it draws the opening snugly against the body. Trust the drafted length instead of measuring the neckline and matching it.
Ignoring the notches on the sleeve cap
The front and back of a sleeve cap are shaped differently, and the single and double notches tell you which edge is which. A sleeve sewn into the wrong armhole, or rotated so the notches do not meet, produces diagonal drag lines from the shoulder that no pressing removes.
Cutting with the stretch running vertically
The grainline arrow on each piece must run parallel to the selvedge, which puts the greatest stretch around the body. Rotate a piece 90 degrees to save fabric and the shirt will strain across the chest while growing longer with every wear.
Sewing knits with a plain straight stitch
A standard straight stitch has no give, so the first time the shirt stretches over the head, the neckline or shoulder seam pops. Use a narrow zigzag, a lightning stitch, or an overlocker for seams, and a twin needle or coverstitch for hems.
Skipping the flat press between steps
Knit seams that are not pressed as you go get locked under the next seam wavy. Press each seam flat with steam before it is crossed by another — especially the shoulder seams before the neckband and the armhole seams before closing the sides.
Where to adjust the fit
Side seams for body width
Try the shirt on after the side seams are sewn but before hemming. Width through the chest, waist, and hip is easiest to change here — take the side seams in or let them out evenly on both sides, tapering to nothing at the underarm so the sleeve is not affected.
Shoulder seam for slope and neckline position
If the neckline gapes at the back or folds collect below the collar, pinch a small wedge out at the shoulder seam near the neck edge. A 5–10 mm adjustment at the shoulder does more for a T-shirt neckline than any amount of work on the band itself.
Sleeve length and hem depth
Pin the hems up at the fold marks and check the lengths in a mirror with your arms relaxed. Sleeve length reads very differently on the body than on the table — adjust at the hem edge only, never at the cap, so the armhole seam stays untouched.
Armhole depth for mobility
If the shirt binds when you raise your arms, the armhole is cutting too low into the body, not too high. Regenerate the pattern with a slightly shorter armhole depth rather than trimming the underarm on the finished shirt — cap and armhole must stay drafted as a pair.
Frequently asked questions
Which line do I cut on — solid or dashed?
Cut on the dashed outer line and sew on the solid inner line. The dashed cutting line already includes the seam and hem allowances you chose in the generator, so nothing needs to be added by hand.
Why is the neckband shorter than the neckline?
So that it lies flat. A knit band stretched onto a longer neckline pulls the opening slightly inward against the body; a band the same length as the neckline has nothing to pull with and gapes. The generator drafts the band at roughly 80–85% of the finished neckline, adjusted for the opening you chose.
Can I sew the generated T-shirt from a woven fabric?
Not directly. The block is drafted with negative or minimal ease that relies on knit stretch, and the neckband finish only works on stretch fabric. For wovens you need a wider body, a deeper armhole, and a facing or binding instead of a band — a bodice-based pattern is the better starting point.
How do I know the sleeve will actually fit the armhole?
The generator runs construction checks on every draft and verifies that the sleeve cap length matches the combined front and back armhole within the intended ease. Match the printed notches — centre to shoulder seam, single notch to front, double to back — and the seam comes together without stretching either edge.
Do I need an overlocker to sew a T-shirt?
No. An overlocker is faster and gives the classic ready-to-wear inside, but every seam in this construction can be sewn on a regular machine with a narrow zigzag or lightning stitch, and hems finished with a twin needle. Knit fabric does not fray, so raw edges do not strictly need finishing.