How to Crochet a Basic Hat
Crocheting a hat is a great way to learn many different techniques of crochet: sc, hdc, dc stitches, how to crochet in the round, how to calculate the size of a hat, & more.
Lets start with a chart. This chart has basic Head Circumference measurements for each age of person & what the Hat Circumference & Hat Height should be for the specific age of the person.

**Tip: when making any crochet item that involves sizing, it is ALWAYS better to get exact measurements of the person than to assume what size to make.

So now that you have an idea of head & hat sizes, lets begin choosing what stitch we want to use.
 Sc (Single Crochet) is the smallest in height of all stitches. Sc will make a firm feeling fabric, with no movement between the stitches. Since the sc is the smallest st, more rounds will have to be made in order to obtain the desired length of the hat. Sc will also produce a hat that has very minimal stretch.
 Hdc (Half Double Crochet) is slightly taller than Sc. Hdc will make a firm feeling fabric, but will have a bit more movement between the stitches than Sc due to the fact that Hdc is a bit taller than Sc. Hdc will produce a hat that has a bit of stretch.
 Dc (Double Crochet) is the tallest of the 3 sts mentioned here. It is double the height of Sc, so in theory how ever many rounds you make in Sc will be half in Dc & vice versa. Dc will make a very moveable fabric that will be slightly holey or lacy due to the normal spaces that are created when working a taller stitch. Dc will also produce a hat that has a good amount of stretch.
These are the basic steps in making a hat (which will be detail below):
 Starting at the Crown, you will start with a basic number of sts & evenly increase stitches in each round to make a flat circle.
 You will keep evenly increasing the stitches on each round of the flat circle until that circle equals the circumference you need for the size of the hat.
 You will then stop increasing stitches & work rounds until the desired length is reached.
In order to determine how many stitches to start with for your first round, the rule of thumb for each stitch is this:

**The reason the total number of stitches to start with is different for each stitch is because of the tallness of each stitch. The Sc will produce a smaller circle, so it needs less stitches to make a complete circle. And so the Dc will produce a larger circle, so therefore needs more stitches to make a complete circle.

In order to properly increase stitches in each round to make a flat circle, the rule of thumb is you must increase the number of stitches you began with for each round. Example, if you started with 6 stitches, then the next round will have 12 stitches, & the next round will have 18 stitches, and so on. This sounds more difficult that what it actually is. but here is a great way to remember it & this works no matter what number of stitches you start with:
 Rnd 1  Starting number of stitches. Ex, 6 (Rnd 1 = 1 stitch in each repeat)
 Rnd 2  2 stitches in each stitch. Ex, 12 (Rnd 2 = 2 stitches in each repeat)
 Rnd 3  (2 stitches in next stitch, 1 stitch in next stitch) repeat. Ex, 18 (Rnd 3 = 3 stitches in each repeat)
 Rnd 4  (2 stitches in next stitch, stitch in next 2 stitches) repeat. Ex, 24 (Rnd 4 = 4 stitches in each repeat)
 Rnd 5  (2 stitches in next stitch, stitch in next 3 stitches) repeat. Ex, 30 (Rnd 5 = 5 stitches in each repeat)
 Rnd 6  (2 stitches in next stitch, stitch in next 4 stitches) repeat. Ex 36 (Rnd 6 = 6 stitches in each repeat)
So let's start to crochet!
In this example, we will make a hat for an Adult Woman that has a 22" head circumference. She would like her hat to fit snug with just a bit of stretch, so we will make the had with Hdc stitches.
Worsted Weight #4 yarn & a 5.5mm hook.
In this example, we will make a hat for an Adult Woman that has a 22" head circumference. She would like her hat to fit snug with just a bit of stretch, so we will make the had with Hdc stitches.
Worsted Weight #4 yarn & a 5.5mm hook.
How to Calculate
the Circumference of your Hat
the Circumference of your Hat
At any time when making the increased flat circle, you can measure the hat to make sure the Circumference of the hat will be accurate. Here is the formula:
So now, you have achieved the Circumference of the hat & you will stop increasing. You will work 1 hdc in each st (no longer putting 2 hdc in a st) to achieve the Length you need for the hat.
 To measure for Length  you can follow the chart at the top of the page. For a Woman's 22" hat  the height should be 7"8". You will measure from the Center of the circle to one edge (the Radius of the circle). At this point, our hat length is 3.5" (or half of the 7" Diameter measurement you measured above for the Circumference).