Top Down Diamonds Preemie Hat

Top down hats scare a lot of knitters, even ones experienced in circular knitting. It's because of the increases needed, I think. However, top down hats are great - if you don't know your gauge you just increase until the diameter is about 1/3rd the desired circumference (C=3.14159D), and then work the hat normally. If you're not sure if you have enough yarn to complete the hat (as happened with this one), you can work it until the yarn is gone and then either add on a new skein for the body (as I did here) or make a beanie. Plus, it feels a lot more like a hat than a tube for the majority of the time!

Finished Size: This is a preemie hat - about 10.5in (16cm) by about 4.5in height (11cm)

Gauge: 13 stitches and 14 rows to 3in (7.5cm) in garter stitch on US5 (3.75mm) needles.

Materials:
Worsted-weight cotton or other soft, washable worsted-weight yarn. (approx. 36yd/33m)
US 5 (3.75mm) double-pointed needles (or whatever method you use for circular knitting)
Darning needle

Abbreviations:
K: Knit
Kfb: Knit through the front & back loops
P: Purl

Instructions:
Cast on 6 stitches.
Row 1: Kfb all stitches (12 stitches).
Row 2 and all even rows: Knit all stitches.
Row 3: (Kfb, k1) six times (18 stitches).
Row 5: (Kfb, k2) six times (24 stitches).
Row 7: (Kfb, k3) six times (30 stitches).
Row 9: (Kfb, k4) six times (36 stitches).
Row 11: (Kfb, k5) six times (42 stitches).
Row 13: (Kfb, k6) six times (48 stitches).
Rows 15 & 17: (P1, k7) six times.
Rows 19 & 23: (P2, k5, p1) six times.
Row 21: (P3, k3, p2) six times.
Rows 25, 27, 29, 31: (P1, k7) six times.
Row 33: (P2, k5, p1) six times.
Row 35: (P3, k3, p2) six times.
Row 37: (P4, k1, p3) six times.
Rows 39 & 41: Purl all stitches.
Row 42: Knit all stitches for one last row.
Bind off in Purl.
Weave in ends.

Note that if you do not wish to have the diamond and triangle motifs, you can just knit in stockinette stitch (or chosen pattern) after row 13. Rows 39-42 create a garter stitch band at the bottom of the hat.