A kids' T-shirt is sewn the same way as an adult one: shoulder seams, neckband, sleeves set in flat, side seams in one pass, then hems. What changes is the proportions. A child's head is large compared with the neck, so the neckline needs a jersey with at least 40 % stretch across and a neckband cut at 80 to 85 % of the opening, and children grow, so choose the size by height and chest rather than age and sew a 3 cm (1 1/4 in) hem you can let down later. A short-sleeved T-shirt for a six-year-old takes about 0.6 m (3/4 yd) of 140 cm (55 in) wide jersey and an afternoon.

The pattern pieces for size EU 38 / US 6, drawn by Sewly's drafting engine (seam allowances included). T-shirt →

Which size should you sew for a child?

Children's sizes are labelled by age, but they are drafted from height: in the European convention, size 2 is for a child about 92 cm (36 in) tall, size 4 about 104 cm (41 in), size 6 about 116 cm (45 3/4 in), size 8 about 128 cm (50 1/2 in), size 10 about 140 cm (55 in), size 12 about 152 cm (60 in) and size 14 about 164 cm (64 1/2 in). A tall four-year-old wears a 5 or a 6. Measure height against a wall, the chest around the fullest part with the tape level, and the arm from the shoulder bone to the wrist with the elbow slightly bent; how to measure a child for sewing explains each one with a wriggling child in mind.

If the height and chest fall in different sizes, cut the chest size and lengthen the body and sleeves to the height. Sewly's T-shirt pattern drafts children's sizes 2 to 14 from the child's own height, chest and arm length, so the length and width come out right together, with the 1 cm (3/8 in) seam allowance it uses on knits already included.

What do you need to sew a kids' T-shirt?

  • Front and back, each cut once on the fold.
  • Sleeves, cut twice.
  • Neckband, a strip cut across the stretch: 80 to 85 % of the neckline length and 6 cm (2 3/8 in) wide for a 2 cm (3/4 in) finished band.
  • Notions: a ballpoint or stretch needle in size 75/11, polyester thread, 6 mm (1/4 in) clear elastic or stay tape for the shoulder seams, and a twin needle for the hems if you have one.

Fabric on 140 cm (55 in) wide jersey, short sleeves: 0.5 m (5/8 yd) for sizes 2 to 4, 0.6 m (3/4 yd) for 6 to 8, 0.8 m (7/8 yd) for 10 to 12 and 1 m (1 1/8 yd) for 14. Long sleeves add about 0.2 m (1/4 yd). A cotton jersey of 180 to 220 gsm with 5 % elastane is the easiest to sew and survives hot washes; interlock is a little more stable for toddlers' clothes; avoid thin single jersey that curls at every edge. Pre-wash at the temperature the shirt will live at, which for children is usually 60 °C (140 °F).

How do you sew a kids' T-shirt, step by step?

  1. Cut with the stretch going around the body. Fold the jersey selvage to selvage, lay the front and back on the fold and the sleeves flat, and cut with a rotary cutter or long scissor strokes so the edges do not drag. Mark the center of each sleeve head and the center front of the neckline with a small snip.
  2. Sew the shoulder seams right sides together with a narrow zigzag (1 mm wide, 2.5 mm long) or the stretch stitch, laying clear elastic or stay tape in the seam so the shoulders do not stretch out when the shirt is pulled over the head. The method for knits on a regular machine is in sewing knit fabrics without a serger.
  3. Make and attach the neckband. Join the short ends of the strip into a loop, fold it in half lengthwise wrong sides together and press lightly. Mark the loop and the neckline in quarters, pin them together at the marks, and sew with the band stretched to fit between the pins, raw edges level. How to sew a neckband on a T-shirt shows the ratio and how to keep the seam flat.
  4. Check the head goes through. Before going further, stretch the neckline over the child's head, or over a tape loop of the head circumference: about 49 cm (19 1/4 in) at 2 years, 51 cm (20 in) at 6 and 53 cm (21 in) at 10. If it is tight, unpick and cut a longer band, or deepen the front neckline by 1 cm.
  5. Set the sleeves in flat. With the body open, match the sleeve head center to the shoulder seam, pin the ends to the armhole corners, and sew from the body side, easing the sleeve in.
  6. Close each side in one seam from the hem up the side, under the arm and down the sleeve to the cuff.
  7. Hem. Turn 3 cm (1 1/4 in) on the body and 2 cm (3/4 in) on the sleeves and stitch with a twin needle or a zigzag, stretching nothing. Press with steam and the shirt is done.
Tip: Press the neckband seam allowance toward the body and topstitch 5 mm (3/16 in) from the seam with the twin needle. It stops the band from flipping up in the wash, which is the first thing to go wrong on a child's T-shirt.

How do you make a T-shirt that lasts more than one season?

Children grow in height faster than in width, so add length rather than cutting a size up: 3 cm (1 1/4 in) extra on the body and 2 cm (3/4 in) on long sleeves, folded into deeper hems that you let down in six months. A shirt cut a full size wider slips off the shoulders and looks borrowed. Choose jersey with good recovery, the kind that springs back when you stretch and release it, so the neckband stays flat after months of being pulled on and off; a ribbed knit for the neckband alone also helps. For a child who hates things over the head, a scoop neckline with a slightly longer band is more comfortable than a round one.

What are the common mistakes?

  • Neckband too long, so the neckline gapes and ripples: recut at 80 %.
  • Neckband too short, so the neckline puckers and will not pass the head: recut at 85 %, or deepen the neckline.
  • Straight stitch on seams: it pops the first time the shirt is pulled on. Use a zigzag or stretch stitch.
  • Hem stretched while sewing, which gives a wavy edge: lighten the presser foot pressure, use a walking foot, or sew over strips of wash-away stabilizer.
  • Choosing the size by age on a tall or small child: measure the height.

When should you sew something else for a child?

For a baby under 2, an envelope neckline or shoulder snaps are easier than a neckband and are outside this pattern. For cooler weather, the same construction in French terry with a ribbed hem band makes a sweatshirt; for summer, choose the sleeveless option of the T-shirt and bind the armholes. If the child wants to help, cutting the neckband and pinning the quarters are safe jobs; sewing with kids lists which steps suit which age.