Single jersey is the thin, drapey knit of most T-shirts and it curls at the cut edges; interlock is a thicker, smoother double knit that lies flat and suits beginners; rib knit has the most stretch and recovery and is the right choice for neckbands and cuffs; French terry is a mid-weight knit with loops on the back for sweatshirts and joggers. Pick jersey for fitted tees and dresses, interlock for easy T-shirts and children's clothes, rib for bands or close-fitting tops, and French terry for sweatshirts and loungewear.
How do the four knits compare?
| Feature | Jersey | Interlock | Rib knit | French terry |
|---|---|---|---|---|
| Construction | Single knit: knit on one face, purl on the other | Double knit: both faces look the same | Alternating knit and purl columns | Single knit with loops of yarn on the back |
| Weight | 120–200 g/m² (3.5–6 oz/yd²) | 180–260 g/m² (5.3–7.7 oz/yd²) | 180–300 g/m² (5.3–8.8 oz/yd²) | 220–320 g/m² (6.5–9.4 oz/yd²) |
| Crosswise stretch | 20–50 %, more with elastane | 20–40 % | 50–100 % or more | 20–40 % |
| Recovery | Good with elastane, poor without | Good | Excellent | Fair to good |
| Edges | Curl toward the right side | Lie flat | Lie flat | Lie flat, slight curl |
| Drape | Soft, fluid | Smooth, more body | Close to the body | Cozy, moderate body |
| Best for | T-shirts, dresses, tanks | T-shirts, kids' clothes, pyjamas | Neckbands, cuffs, fitted tops | Sweatshirts, hoodies, joggers |
The stretch figures are a guide; measure your own fabric by stretching 10 cm (4 in) of it against a ruler. A good pattern states the minimum stretch it needs, so check the fabric against it before you cut.
What is jersey and what is it good for?
Jersey is a single knit: every stitch is made the same way, so one face shows V-shaped knit stitches and the other shows purl bumps. It is the thinnest and most fluid of the four, and the one most ready-to-wear T-shirts are made from.
Pure cotton jersey is cool and soft but has little recovery: a neckline or waistband grows with wear. Cotton jersey with 3–5 % elastane (often sold as "cotton spandex jersey" or "stretch jersey") snaps back, holds a neckline and makes a much better fitted top or dress. Viscose jersey is drapier still, perfect for wrap dresses and gathered tops, and the hardest to sew because it stretches under its own weight.
Jersey's one annoying habit is curling: the cut edges roll toward the right side crosswise and toward the wrong side lengthwise. Starch the edges, use weights rather than pins, and do not let a cut piece hang off the table.
What is interlock and why is it good for beginners?
Interlock is a double knit: two layers of single jersey knitted together so that both faces look like the smooth knit side. It is thicker, more stable and more opaque than jersey, the edges stay flat, and it does not shift on the table.
Those qualities make interlock the easiest knit to learn on. It feeds through a regular machine without a walking foot, a zigzag seam looks tidy on it and a neckband can be cut from the same fabric. The trade-off is drape: interlock has body, so it suits a straight T-shirt, a boxy top or a child's leggings better than a clingy dress. It is also warmer than jersey of the same fiber.
What is rib knit and where should you use it?
Rib knit alternates columns of knit and purl stitches, so the fabric folds in on itself and can stretch far crosswise and spring back. A 1×1 rib (one knit column, one purl column) is fine and firm; a 2×2 rib is more pronounced. Many ribs are sold with elastane for extra recovery.
Rib is the fabric for anything that has to stretch over something and then hug it: neckbands, cuffs, hem bands and waistbands on sweatshirts and hoodies. A neckband cut from rib is usually cut 15–20 % shorter than the neckline, so it pulls the neck edge snug. Rib also makes lovely fitted tanks, turtlenecks and close-fitting tops, with the body of the garment cut from the same rib.
Sold as "ribbing" in narrow tubular widths of about 50–70 cm (20–28 in), or as full-width rib by the meter.
What is French terry and how does it differ from sweatshirt fleece?
French terry is a single knit with a smooth jersey face and small loops of yarn on the back. The loops trap air, so it is warmer than jersey while still breathing, and it is absorbent. Weights run from a light 220 g/m² (6.5 oz/yd²) summer terry to a 320 g/m² (9.4 oz/yd²) heavyweight.
Sweatshirt fleece is French terry that has been brushed on the back until the loops become a soft fuzzy nap. It is warmer and bulkier, stretches less and pills more easily. French terry is the better choice for a sweatshirt you will wear in spring and autumn, for joggers and for a lined hood; fleece for winter.
French terry with 5 % elastane recovers better at the knees and elbows. A terry without elastane bags out there, which matters for joggers more than for a sweatshirt.
Which needle, stitch and seam allowance do knits need?
All four need a ballpoint or stretch needle (the rounded tip slides between the loops instead of piercing them), polyester thread and a stitch that stretches: a narrow zigzag, a lightning stitch or a serger. The guide to sewing knit fabrics on a regular machine shows the settings.
Seam allowances on knits are narrower than on wovens because the edges do not fray and a wide allowance adds bulk: 1 cm (3/8 in) is standard, and serged seams are often trimmed to 6 mm (1/4 in). Sewly's knit patterns use 1 cm by default, adjustable, so a serger seam matches the pattern without trimming.
Hem with a twin needle, a coverstitch or a zigzag, and stabilize shoulder seams with clear elastic or a strip of fusible tape so they do not stretch out.
Which should you choose?
- A fitted T-shirt, tank or T-shirt dress: cotton jersey with elastane, 160–200 g/m² (4.7–6 oz/yd²). Drape, recovery and a neckline that stays put. The T-shirt pattern is drafted for this weight.
- A first knit project: interlock. Flat edges, no curling, easy to feed.
- Children's T-shirts and pyjamas: interlock or a sturdy cotton-elastane jersey; both survive the washing machine.
- Neckbands, cuffs and waistbands: rib, cut shorter than the edge it finishes. On a lightweight tee, self-fabric jersey with elastane also works.
- A fitted long-sleeved top or turtleneck: rib knit, with negative ease.
- A sweatshirt, hoodie or joggers: French terry, 250–300 g/m² (7.4–8.8 oz/yd²), with rib for the bands. Choose brushed fleece only for cold weather.
- A drapey wrap dress or gathered top: viscose jersey, once you are comfortable with cotton jersey.
Whatever you choose, buy 10–15 cm (4–6 in) more than the pattern asks for and prewash it: knits, especially cotton ones, shrink more in length than in width.