A well-known fact about me is my ongoing and eternal love of pie. I have never met a (dessert) pie that I didn't like, and am unable to pick just one favorite. Apple? Berry? Key lime? Chess? Pecan? Peach cheesecake? Sweet potato? But I also love the mathematical constant pithat is, the ratio of the circumference of a circle to its diameter, or 3.1415926535 (and so on). Math team cheers need it, calculations of distance, momentum, and volume need it in every branch of math, science, and engineering, and it's fun to yell at sporting events when there's 3:14 left on the timeclock. This hat uses the principle of pi in two ways. First, it is worked top-down with increases worked until the diameter of the knitting is 1/3.14 of the desired circumference. Second, the welting pattern of alternating knit and purled bands follows the digits of pi! The sample shown uses approximately 80 yards of bulky weight yarn, spun and N-plied from past PhatFiber Sampler Box fluff samples. This is a great project for such "monster yarn" - but it would also look great in a more normal handspun or commercially made yarn. BASIC SKILLS NECESSARY Knitting in the round Knit & purl patterning GAUGE 11 stitches and 16 rows = 4 inches in stockinette stitch SIZING / FINISHED MEASUREMENTS Fits adult heads 21-24"