How to make a baby sleep sack

1. Materials & tools

Materials (size 1–2 years)

• Main fabric (six-layer gauze, fleece or quilted cotton) — about 100 × 110 cm (39 × 43 in)
• Lining fabric (the same, or plain cotton) — the same amount
• Bias tape for the neckline and armholes — about 150 cm (59 in)
• Snap fasteners — 4–6 sets (the pattern notes give the number)

Tools

• Sewing machine (or needle and thread)
• Fabric marker or pencil
• Ruler and scissors
• Iron
• Pins or clips

2. Make the pattern (auto-generated in Katagami)

With the Katagami pattern tool, you just enter the finished size and it drafts a seam-allowance-included pattern, tiled to print at actual size on Letter or A4.

1. Open the tool
   Open the pattern tool and choose “Baby” → “Baby sleep sack” from the tabs at the top.
2. Enter the size
   Enter chest, length, shoulder width, neck width, armhole depth, hem flare and ease. Enter the baby's own chest; it is worn over clothes, so the pattern adds the ease. Presets cover newborn to 3 years.
3. Set the seam allowance
   Use the slider at the bottom (beginners: 1.0–1.5 cm / about 3/8–5/8 in).
4. Print
   Press “Print (actual size)”, then in the print dialog set Scale = 100% and turn “Fit to page” OFF. Check the 50 mm calibration box on the first guide sheet with a ruler.

3. Cutting the fabric

1. Trace the pattern
   Trace the back (on the fold) and the two fronts.
2. Cut
   Cut the back and both fronts in outer and lining. The fronts have an overlap beyond the center front; transfer the center-front notches, which mark the snaps.
3. Finish the edges
   Everything is enclosed between two layers, so no edge finishing is needed.

4. Sewing

4-1. Assemble the outer and the lining

1. Sew the outer fronts to the outer back at the shoulders and sides.
2. Assemble the lining the same way.

4-2. Join outer and lining

1. Place them right sides together and sew around the front edges and the hem, leaving a 10 cm (4 in) gap to turn through.
2. Trim the corners, turn through the gap, press and close the gap.

4-3. Bind the neckline and armholes

1. With outer and lining now behaving as one layer, bind the neckline and both armholes with bias tape.

4-4. Add the snaps

1. Lap the fronts at the center front and fit a snap at each center-front notch — the stud half on the top front, the socket half on the under front.

✏️ Place the top and bottom snaps first, then divide the space between them evenly — snaps spaced by eye always drift. Leave the neck one loose enough not to press on the throat.

5. Tips & variations

• Season by fabric: single-layer gauze for summer, lined fleece or quilted cotton for winter. Same pattern either way.
• Wide at the hem: a generous hem flare lets the legs move when the baby rolls over.
• Make two: it is used every night, so one is always in the wash.
• Interfacing behind the snaps: on soft gauze, fuse a narrow strip of interfacing inside the overlap so the snaps do not pull out.