I have recently ventured into the depths of hat making. While I am familiar with crocheting in circles, from amigurumis to bags, I do not exactly needed them to be sized perfectly. And I had always have a nice pattern to follow or just used the simple working in the rounds rules for hats. So when the hat I recently made didn’t fit the intended recipient, I was a bit disappointed. Even though the measurements seems right on paper, it just didn’t fit!
Some of the elements that could create variance from patterns to our end results are the yarn used and tension we handled. So to ensure we get the desired size, we usually depend on the gauge provided by the designer. I have uncovered several standard formulae we can refer to so we can crochet hats of just about any sizes.
Before everything, measure your head! You should measure where you want your hat to sit/end. Take 1~2cm off to get the circumference of your hat so it hugs your head snugly.
Hat Base
The foundation of hats is the crown – the increment rounds before working on the heights – and the way to determine how big that is, is simple math:
Diameter = Circumference of Hat ÷ pi (i.e. 3.14)
E.g.
Circumference of Head | 32 cm |
Circumference of Hat | 31 cm |
Diameter of Crown | 31 cm ÷ 3.14 ≈ 10 cm |

We can work up the crown base in any ways we like as long as we reach the desired diameter. For this, I use the working-in-the-round rules, with beginning rounds of either:
6 Single Crochet; or
8 Half Double Crochet; or
12 Double Crochet, etc
We may reach the same base size with different stitches; HDC in 5 rounds and DC in 3 rounds may both get you a circle with 9~10 cm in diameter. I would suggest composing with more stitches in a round. I find the base curves into the height softer than with lesser stitches.
Or to be more specific, work out your gauge and calculate accordingly.
E.g.
Circumference of Hat | 32 cm |
Gauge | 2 stitches/cm |
Diameter of Crown | 32 cm × 2 = 64 stitches |
Hence you would want to work up 64 stitches for a 32 cm circumference, i.e. 8 rounds beginning with 8 HDC.
Hat Height
Height = Circumference of Hat × 0.4
E.g.
Circumference of Hat | 31 cm |
Diameter of Crown | 31 cm × 0.4 ≈ 12 cm |

This is a simple formula to get standard height but we may want to wear our hat differently; slouching or above the ears. You can ± 1 or 2 cm for desired fashion.
And finally, not only to add on to the many charts on the net, I’d inserted the formulae on Sheet; you may save a copy and simply enter the head measurements each time you need to work on one!
Now that you are equipped with these basics of crocheting hats, go on and try out my new design, the Claris Beanie.
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