Sew a classic crew-neck sweatshirt

A crew-neck sweatshirt is five pieces: a front, a back, two sleeves and three strips of ribbing for the neckband, the cuffs and the hem band. You sew the shoulders, attach the neckband stretched to fit, sew the sleeves in flat, close each side and underarm in one seam, then add the cuffs and hem band. With a medium-weight French terry, a stretch needle and a narrow zigzag, the whole project takes an afternoon.

What do you need to sew a sweatshirt?

The pieces of a classic crew-neck sweatshirt:

• Front and back, each cut once on the fold.
• Sleeve, cut twice, with the back of the sleeve cap marked by a double notch.
• Neckband, one strip of ribbing cut across the stretch, shorter than the neckline it goes on.
• Cuffs, two strips of ribbing, and a hem band, one longer strip, all rectangles you can measure straight onto the fabric.

Notions are short: a ballpoint or stretch needle in size 80/12 or 90/14, polyester thread, and ribbing. A hip-length sweatshirt in a women's medium takes about 1.6 m (1 3/4 yd) of 140 cm (55 in) wide French terry, and a relaxed or oversized fit takes up to 2 m (2 1/4 yd). The ribbing needs a piece about 40 × 50 cm (16 × 20 in), which is enough for the neckband, both cuffs and the hem band of most sizes.

Which fabric should you use for a sweatshirt?

The main fabric should be a stable knit with some stretch across the width and good recovery. French terry, with its smooth face and loops on the back, is the classic choice at 240 to 300 g/m² (7 to 9 oz/yd²). Brushed-back sweatshirt fleece is warmer and a little thicker; an organic cotton sweat with 5 percent elastane keeps its shape best over time.

The bands should be true rib knit, 1×1 or 2×2, because ribbing stretches further than the body fabric and springs back. Cuffs cut from French terry work when the fabric recovers well, but a cuff cut from a sloppy knit stays stretched after the first wear. Pre-wash everything: cotton knits can shrink 5 percent, and the ribbing often shrinks more than the terry.

How long should the neckband, cuffs and hem band be?

Bands are cut shorter than the edge they finish, then stretched to fit as you sew. The stretched band pulls the opening in, which is what keeps a crew neck lying flat against the collarbone and a cuff snug around the wrist. Measure the finished edge on the pattern, without the seam allowances, and apply a ratio:

Add 2 cm (3/4 in) to each cut length for the two 1 cm (3/8 in) seam allowances where the strip is joined into a loop. Cut the strips with the ribs running across the short side, so the stretch runs along the length of the band. A very stretchy ribbing can go to the lower end of each range; a firmer one needs the upper end, or the neckband will stand away from the neck in a ripple.

Tip: Before sewing the cuff to the sleeve, check that the loop stretches over your hand. If it does not, cut it a little longer; a cuff you cannot get your hand through is the most common reason a first sweatshirt goes unworn.

How do you sew a crew-neck sweatshirt, step by step?

Set the machine to a narrow zigzag, 1 mm wide and 2.5 mm long, or a lightning stitch, so every seam stretches with the fabric. A serger with four threads does the same job faster. Seam allowances are 1 cm (3/8 in) throughout.

1. Sew the shoulder seams. Place the front and back right sides together and sew both shoulders. Press the allowances toward the back. On a loose knit, stitch a strip of clear elastic or fusible stay tape into the shoulder seams so they cannot stretch.
2. Make the neckband. Fold the strip in half across its length, right sides together, and sew the short ends to make a loop. Fold the loop in half along its length, wrong sides together, and press. Mark the loop in quarters with pins.
3. Attach the neckband. Mark the neckline at the center front, center back and shoulder seams. Pin the band's quarter marks to those points with the seam at the center back, raw edges together on the right side. Sew with the band on top, stretching it between each pair of pins until it lies flat on the neckline, and let the feed dogs move the body fabric without stretching it. Press the seam allowance down toward the body and, if you like, topstitch it with a twin needle.
4. Sew the sleeves in flat. With the body open, match the center of each sleeve cap to a shoulder seam, right sides together, and the double notch to the back. Pin the ends, then the middle, and sew with the sleeve on top. There is almost no cap ease in a sweatshirt sleeve, so the edges should match without gathering.
5. Close the sides. Fold the sweatshirt right sides together so the front and back meet along one side and the sleeve meets itself along the underarm. Sew from the cuff edge to the hem in one seam, matching the armhole seams exactly. Repeat on the other side.
6. Attach the cuffs. Make each cuff loop as in step 2, mark it in quarters, pin it inside the sleeve end right sides together with the seam at the underarm, and sew while stretching the ribbing to the sleeve.
7. Attach the hem band. Make the band loop, divide it and the hem in quarters with the band's seam at one side seam, and sew it on in the same way.
8. Press every band seam with the allowance toward the body, using steam and a lift-and-set motion rather than dragging the iron across the ribbing.

Finishing the band seams is optional on a knit, since it does not fray. If the allowances look untidy inside, trim them to 6 mm (1/4 in) after sewing, or run them through a serger.

What are the common mistakes when sewing a sweatshirt?

• Stretching the body instead of the band. The band is the only piece that should be under tension. If the neckline ripples, the body was pulled through; if the band buckles, it was not stretched enough.
• Using a universal needle. A sharp universal point can pierce and cut the knit loops, which shows up later as small holes along the seam. A ballpoint or stretch needle pushes the loops aside.
• A straight stitch on the seams. It pops the first time the sweatshirt is pulled over the head. Use a stretch stitch or a narrow zigzag, and sew the cuff and neckband seams twice if you are unsure.
• Cutting the ribbing in the wrong direction. The ribs must run across the band's width so the stretch goes along the length.

The guide to sewing knit fabrics covers needle, stitch and presser foot settings in detail, and the post on sewing a T-shirt neckband shows the quartering method close up.

Can you draft the sweatshirt to your own measurements?

The sweatshirt and hoodie pattern on Sewly drafts the front, back and sleeve from your chest, shoulder and arm length, in a regular, relaxed or oversized fit and five lengths from cropped to tunic, and gives the neckband, cuffs and hem band as cutting dimensions already shortened for ribbing. The sewing guide lists the ribbing and fabric quantities for 110, 140 and 150 cm (45, 55 and 60 in) wide fabric, and you can ask it a question at any step. If you want a hood and a kangaroo pocket instead of the crew neck, the hoodie project post picks up where this one ends.