How to Shape the Top of a Hat

From The Knitting Fiend. Guess what? I'm compiling an index of calculators here.

This page will calculate the ideal decrease rate to shape the crown of a hat using paired decreases; the ideal rate results in a fairly flat crown. The "theory" may, eventually, be discussed at my blog.

Seasoned hat knitter will notice that if you enter a typical gauge for a hat with 6 or 8 wedges, the calculator reproduces the "rule of thumb" shaping for a hat. However, the calculator can be used to determine the proper shaping for triangular hats (three wedges), square hats, or a larger number of wedges typical of those in various tams, including the beautiful ones in this book: Knitted Tams

You can also shape hats tops using single increases; these form spirals wedges and I love them. However, I'm not going to discuss the theory for spirals because, the complete theory is too complicated. As a general rule, if you want spiral top, you want it to be flat, knit at least 6 spirals, you can use the shaping suggested here, but enter half the number of spirals here you want. (So, if you want 6 spirals, enter 3 here.) Work only 1 decrease per round. The calculation isn't perfect, but it will be ok.

Most or you are going to think "it can't be this complicated". It's not. I'll discuss reality a bit at the end.

Enter number "wedges" you want on the crown. (The schematic shows 6.)	wedges.
Enter number of stitches around the unshaped part of the hat. (If you are knitting bottom up, this is the number of stitches before you begin shaping. For this program, this must be a multiple of the twice the number of wedges. The program will round for you.)	stitches.
Enter number of stitches per inch.
Enter number of rows per inch.
Based your input, the hat circumference will be:	stitches.
To create the flattest possible hat, the crown must have the number of rounds indicated to the right.	rounds
You will decrease the number of times indicated to the right: (Note: if the number of times you decrease is greater than the number of rows, you will not be able to knit the hat using the directions below.)	times

You will find three methods to shape the hat crown below. None are complete hat patterns, but you can use them to design your own. The instructions assume you know to cast on and do whatever you want to do for the bottom of the hat, which is usually an unshaped tube. If you follow the instruction, the hat will measure inches from the hem. To make a shorter hat, start shaping the crown earlier; to make a longer hat, shape later.

When you finish knitting the lower part of the hat, you will need to distribute markers evenly around the top of the hat; make 1 of then a different color for the other, and call that marker 1. There will be stitches between each marker. Afterwards, you will shape by alternating decrease and plain rounds. Work these as follows:

Plain rounds: Begin 2 stitches before marker 1. Knit all stitches in round.
Decrease round: Begin 2 stitches before marker 1, k2 together, slip marker, ssk, knit until 2 stitches remain before next marker. Repeat times. The next round begins 2 stitches before marker 1.

Note that for all three shaping rates, stitches remain in each wedge after the final decrease round.

Hang a row marker, then select any one of these:

Paired increases, approximate shaping, good enough fit.

Knit until the hat measures inches from the hem. Place markers.
Do this times: Work 1 decrease round; work plain rounds.
Work 1 decrease round.
You will have knit rounds, which is fewer than ideal. The length from the row marker to this point will be approximately inches.
Note: If there there are way too many fewer rows knit than required for an absolutely flat crown, the top of the hat may look a bit gathered up. It's unlikely you or anyone else will notice; knitting stretches and the top of the hat will look flat. This is ok, and often hats are worked with no decreases at all, you just knit to the depth you want and gather up the top.

Paired increases, approximate shaping, good enough fit.

Knit until the hat measures inches from the hem
Do this times: Work 1 decrease round ; work plain rounds. Place markers.
Work 1 decrease round.
You will have knit rounds, which is more than ideal. The length from the row marker to this point will be approximately inches.
Note: If there are many more rows knit than ideal, the top of the hat will look a little pointy. However, doesn't matter for most hats, people's heads aren't actually flat. You've probably figured out that if you want a very pointy hat, you can just work extra rounds between decreases. I could do the math to tell you how many, extra rows for a certain height of hat, but sorry, not today!

Paired increases, excessively precise shaping that would only be knit by a compulsive knitter. This might be worth it if you are felting and want a very flat hat top. It also mightbe worth the trouble for a beret. If you are working a skull cap, work these in the order suggested. If you are working a beret, and really want to be compulsive, reorganize the instructions and intersprese slow decrease rates between the fast decreases. That makes it flatter. (But it really doesn't matter.)

Knit until the hat measures inches from the hem. Place markers.
Do this times: Work 1 decrease round; work plain rounds
Do this times: Work 1 decrease round; work plain rounds
Work 1 decrease round.
You will have knit rounds, which is equal to the ideal number for a flat as a pancake hat with this number of wedges. The length from the row marker to this point will be approximately inches.

Finish up: For all hats, break yarn leaving a long tail. Thread at tapestry needle and thread through open loops. Pull tight to close hole. Weave in all ends, block as appropriate for your yarn, and wear.

Now for a dose of reality!

This program calculates the shaping for you, and it can be a real help if you want to reality check a published pattern. You can see there are at least three perfectly good ways of shaping the top of the hat. You will likely be perfectly happy with any one of these shapings. You will also find other "good enough" shaping methods in patterns. The reason they all make perfectly acceptable crowns is that knitting stretches. On the one hand, you don't want to be way off, but on the other hand, you don't need to shape the top of the hat perfectly. There is a range that will result in fairly flat hat tops.

Here are some good reasons to shape differently:

If you don't want to switch to double pointed needles, you can start your decreases late, decrease until you would be forced to change to DPN's and just gather the stitches that reamin. The center doesn't look too gathered; there is one hitch: when designing the hat, you need to account for the fact that the crown is shorter than it would be if you kept shaping until you had very few stitches left. (I do this on Teddy's beret.)
If you want to write very, very simple instructions with few gathers, and don't care that the amount of pointiness will vary for different hat sizes or different gauges, and don't care how many wedges you have. You can just decide everyone is going to decrease "x" times. Period. ( I do this on my roll brim hat. )
You want to fit a fancy fair-isle pattern, into each wedge, you can adjust the number or plain rounds between decreases to fit in some motif. As long as your shaping falls somehere near the shaping described here, your hat will look fine. (I haven't designed an example.)

Have fun knitting!
Lucia