The first thing you have to do is to find out the head circumference. It is easy if you planning to crochet a hat for yourself or a family member – just measure the head. Use the head circumference to calculate the diameter of the bottom of your hat.

Diameter = head circumference / 3.14

NOTE!
If you want the hat to fit snugly, deduct 0.5-1.5 cm from the diameter. Do not deduct if you are planning to crochet your hat with single crochets only.
The exact number depends on a density of your crochet, chosen pattern and yarn.

There is a one more number that we need to find out and that is the hat height. Measure the head from ear to ear through the top, divide by two and add 1 to 3 cm depending on how much you want the hat to cover the ears.

If you can’t measure the head circumference here is a table with average sizes to help you:

Now we know all the sizes and measurements and we can start to crochet. We start with crocheting a flat round which is the bottom of the hat. Here are several common rules to do it:

• If you want to make your hat’s bottom with single crochets, start with 6 single crochets in a first round and as you crochet add 6 more single crochets in each round.
• If you want to make your hat’s bottom with half double crochets, start with 8 half double crochets in a first round and as you crochet add 8 more half double crochets in each round.
• If you want to make your hat’s bottom with double crochets, start with 12 double crochets in a first round and as you crochet add 12 more double crochets in each round.

Here are illustrations to show you different ways to make increases in each round: 

1. Increase is always at the end of a sector. You will get a hat with symmetrical sectors and visible increase lines.

2. Increase is always at the beginning of a sector. You will get a hat with asymmetrical sectors slightly curved to the right and visible increase lines.

3. Increases are randomly placed. You will get flat circle with no visible increase lines.

It is up to you and your imagination to pick the method you will be using.

Once the method is picked start to crochet the bottom. After you reached a diameter of 12 cm start to make increases in every other round (instead of every round). That way you will get a nice round shape of your hat. Continue in rounds until you reach the desired diameter that we calculated before. Once the diameter is reached continue to crochet in rounds without increases until you reach the desired height.

The hat is ready. You can decorate it, add ears for warmth or wear it just the way it is.