Pi Hat Recipe

Not pie. Pi. As in 3.14159…..

Today I am sharing my simple, just-a-little math, any-gauge, any-yarn, top-down, knit-in-the-round hat recipe that I use over and over. You’re welcome.

Step one: determine desired head size of recipient. Measure them, if possible. Take into account hair volume, too – folks with curly or thick hair need a bit more room than those without. Nobody likes “hat hair”.

Roughly, infant/baby = 16-18″, child = 18-20″, women = 20-22″, men = 22-24″ (varies widely, of course; I have a large cranium at 22.75″; but then, nobody ever accused me of being dainty…).

Most hats should fit snugly, so deduct 1-2″ from the actual head size. I’m making a hat for someone with a 24″ head, so I’ll be making a 23″ hat that is 10.5″ tall from crown to brim (more on hat height in step four below).

Still with me?

Step two: find a calculator. Your phone probably has one. The internet definitely does. Take desired circumference of hat (say, 23″) and divide it by Pi – 3.1416 – which, in this example, equals 7.33. That’s the diameter (in inches) that you want before you begin knitting straight. Round down to a measurable number. I’ll use 7.25″.

Step three: cast on 8 stitches with desired yarn and appropriate needles. (hint: the ball band will give you recommendations) You can use circulars or DPNs, your choice. Increase every other round in the method below until the hat is at your desired diameter as determined in step two.

Sidebar: Increases can be whatever you like. I usually do a lifted increase, but you can KFB or even just YO. I will be knitting in stockinette, but if you’re feeling tricky you can substitute in a stitch pattern, cable, or rib the whole hat. Just remember that different stitches will affect the stretchiness of the hat, so you may have to adjust sizing.

For beanie-type shaping, follow this increase example:

CO 8 and divide as necessary on your needle(s). Join, being careful not to twist, mark the beginning, and begin knitting in the round:

  1. (M1, k1) around
  2. Knit
  3. (M1, k2) around
  4. Knit
  5. (M1, k3) around
  6. Knit
  7. (M1, k4) around
  8.  Knit

You will be increasing 8 stitches every other round, in a slight spiral pattern on the crown. Continue in this fashion until your circle is the desired diameter. Just lay the hat out flat on a table and take your best measurement across the center with a ruler.

Step four: knit round and round without increases until the hat is 2 inches less than desired height.

The total hat height from brim to crown should be half of the circumference minus 1-3 inches depending on the desired fit / how much ear coverage you want. If you do “circumference divided by two minus one” you will get a hat that covers the ears. “Minus two” will hit mid-ear, and “minus three” will be a small beanie that ends just above the ears. On the other end of the spectrum, if you want a folded brim or a slouchier fit, make it a little longer.  And again, consider hair volume as this will definitely affect the fit. Poofy hair requires a taller hat.

I will knit my hat to 8.5″ tall (circumference divided by two minus one) before beginning the ribbing in step five.

Step five: for a 2X2 ribbing (that’s K2, P2 around) at the brim you need a number divisible by 4. If you cast on 8 like I told you and didn’t mess up the increases anywhere, you will be fine. I like to decrease out 4 or 8 stitches in the final round of stockinette to prevent the ribbing from being too loose. You can also go down a needle size or two to create a firmer ribbing. Do both, or neither. Your choice. (You can also, of course, use a 1X1 ribbing, a twisted rib, seed stitch, or just keep on with the stockinette and have a rolled brim.)

Knit the 2X2 ribbing for 2″ and bind off in pattern and somewhat loosely, using a larger needle if necessary to keep it from cutting the circulation off.

Step six: Using the cast-on tail, close the little hole on top of the hat by threading the yarn through the initial cast-on stitches and pulling tight. Weave in ends on inside of hat. Block if desired.

Notes: if you want a longer / pointier / less rounded top on the hat, just do more rounds of knitting between the increase rounds (this will make measuring the diameter a little trickier, so you might have to actually use a gauge measurement instead of diameter). You can also cast on a larger number of stitches (say, 24) and then gather the top and add a sassy pompom for a more retro ski-hat look. If you want a slouchier hat, knit the top a bit bigger than the head and then decrease more for the ribbing (to keep the hat from falling off). Knit stripes, use up leftover yarns, hold two strands together for a thicker hat, add tassels or a pompom to the top. Use your imagination!

About wonkydonkey

You want random? You got it. Mostly knitting and gardening, with some home improvements, pets, baking, family, and the occasional bad joke thrown in for good measure.
This entry was posted in Knitting & Crochet, Ravelry. Bookmark the permalink.