Most sweater patterns use one of three constructions: raglan, set-in or drop-shoulder. They are not interchangeable, even when the finished chest measurement is the same. The construction decides where the garment is wide, where it is shaped, and how the sleeve sits on the shoulder.
If you are choosing a pattern, choose the construction that matches the fit you want — not just the size.
The three constructions
| Construction | Armhole | Sleeve | Seaming | Fit |
|---|---|---|---|---|
| Raglan | Diagonal lines from underarm to neck | Worked from the neck down or picked up | Little or none | Follows the shoulder; easy to lengthen |
| Set-in | Curved armhole with a sleeve cap | Separate sleeve, seamed in | Shoulder and side seams | Tailored; closest shoulder fit |
| Drop-shoulder | Straight, with no armhole shaping | Straight tube, seamed at the shoulder | Shoulder and side seams | Boxy; more ease at the armhole |
Raglan
Raglan shaping runs diagonally from the underarm to the neck. It can be worked top-down in one piece or bottom-up, and it often needs little or no seaming. The diagonal lines are forgiving across shoulder shapes, and it is easy to lengthen the body or sleeves.
The trade-off is that the raglan line draws attention to the shoulder and can add visual width. The fit is less tailored than a set-in sleeve.
Set-in
A set-in sleeve has a curved armhole and a shaped sleeve cap that is seamed into it. It gives the closest, most tailored shoulder fit, which is why it is common in fitted garments and jackets. It also requires the most accurate armhole and cap maths.
If the cap and armhole do not match, the sleeve will pucker or the shoulder will sit oddly. Set-in construction rewards a schematic and a careful gauge.
Drop-shoulder
A drop-shoulder has a straight armhole and a straight sleeve tube; the sleeve seam sits below the natural shoulder. It is the simplest construction to knit and grade, and it produces a boxy, relaxed fit. It needs more ease at the armhole to allow movement.
It is a good choice for a first sweater, a loose garment, or a design where the fabric is the focus rather than the shoulder shape.
A worked example
Body chest 100 cm, 8 cm of positive ease, finished chest 108 cm.
- Raglan: the 108 cm chest is distributed around a yoke; the armhole depth and the neck shaping control the fit. Easier to modify the length.
- Set-in: the body and sleeves are separate; the armhole depth, cap height and upper-arm width all need to agree. Better for a tailored look.
- Drop-shoulder: the body is a straight tube; the sleeve is a straight tube; the shoulder seam sits wide. The same chest measurement feels looser because of the armhole shape.
The chest number alone does not tell you how the garment will feel. The construction does.
Which to choose
- First sweater: drop-shoulder or a simple raglan, with a forgiving gauge.
- Tailored fit: set-in, with a schematic and a careful armhole.
- Colourwork yoke: raglan or circular yoke, where the pattern follows the shaping.
- Loose, boxy garment: drop-shoulder, with enough armhole ease.
What about a circular yoke?
A circular yoke is a fourth common construction: the body and sleeves are joined and the yoke is worked in the round with increases. It suits colourwork and produces a seamless garment, but the fit depends on the yoke depth and the increase rate. It is closer to a raglan in construction than to a set-in sleeve.
Limits
Construction names describe the armhole and sleeve, not the whole fit. Ease, length, gauge and fabric still decide how the sweater wears. A boxy drop-shoulder in a drapey yarn behaves differently from the same construction in a dense wool.
For the numbers behind the diagram see reading a schematic and body measurements.