Any-Size Elf Hat
Supplies: Yarn and needles to knit to the gauge of about 4 stitches to the inch in a k1-p1 rib. This should be about a standard worsted-weight yarn on size 7 or 8 needles. You should be able to knit any size hat with about 4 ounces of yarn.
Measure the intended wearer's head. Subtract 1 inch and multiply the result by 4. For example, if the head is 21 inches, subtract 1 for 20 inches, multiply by 4, for a result of 80 stitches. Cast on that number of stitches in the main color. Knit in a k1-p1 rib for 1 or 2 inches. Knit in stocking stitch until work measures 7 to 9 inches from the start.
At this point you will be knitting the rest of the hat in stocking stitch. Every 12 rows decrease 8 stitches spreading the decreases evenly across the row. It is very handy to make this hat in stripes to use up scraps of yarn, and to make the stripes 6 rows each. This way it is easy to keep track of the decrease rows. When you get down to between 8 and 12 stitches knit the last 12 rows and then cut the yarn drawing it through the last stitches tightly and knotting and anchoring it securely. If you knit this hat on two needles you will want a long enough tail to sew your side seam, if you knit it in the round you will only need a long enough tail to sew on the pom-pom or tassel on the tip.
Make a matching pom-pom or tassel and sew it on the tip, then if you have a seam, sew it. Fold over the k1-p1 rib to form the brim. Tah-dah.
If you have any trouble at all with this pattern, just ask.
An example: Adult woman's size, 21-inch diameter head: In standard knitting worsted weight yarn on size 7 needles, cast on 80 stitches. Work 1.5 inches in k1-p1 rib. Work the next 6.5 inches in stocking stitch. [The work should now measure 8 inches from cast on.] At this point you will be knitting the rest of the hat in stocking stitch. Decrease 8 stitches evenly over row on every 12th row until 8 stitches remain. Work last 12 rows, then cut yarn and thread through the last 8 stitches. If you worked this pattern on two needles leave enough of a tail to sew the side seam after sewing on a tassel or pom-pom. The tassel or pom-pom should be made of the same yarn.
For spinners: This hat can be made in any weight yarn as long as you adjust the cast-on.