Crochet Hat Size Calculator
Get the right size for any head, from preemie to adult: hat circumference, crown size, stitch counts and rounds.
Crochet hat size chart
Typical head sizes and hat measurements. The hat circumference includes about 10% negative ease so it stays on.
| Size | Head | Hat circumference | Crown diameter | Hat height |
|---|---|---|---|---|
| Preemie | 12 in | 10.8 in | 3.4 in | 4.5 in |
| Newborn | 13.5 in | 12.2 in | 3.9 in | 5.5 in |
| 0–3 months | 14.5 in | 13.1 in | 4.2 in | 6 in |
| 3–6 months | 16 in | 14.4 in | 4.6 in | 6.5 in |
| 6–12 months | 17.5 in | 15.8 in | 5 in | 7 in |
| Toddler | 18.5 in | 16.7 in | 5.3 in | 7.5 in |
| Child | 19.5 in | 17.6 in | 5.6 in | 8 in |
| Teen / small adult | 21 in | 18.9 in | 6 in | 8.5 in |
| Adult (average) | 22 in | 19.8 in | 6.3 in | 9 in |
| Adult large | 23 in | 20.7 in | 6.6 in | 9.5 in |
Heads vary, so measure when you can. For a slouchy hat add 2–3 inches of height.
How to size a crochet hat
Top-down hats start with a flat circle. Keep increasing until the circle's diameter equals the hat circumference divided by π (about 3.14), then work even rounds until the hat is tall enough.
Brim-up hats start with a chain as long as the hat circumference. Work even until you're about one crown-radius short of the full height, then decrease evenly to close the top.
Your gauge decides the stitch counts, so crochet a small swatch with the yarn and hook you'll use and measure it before you start.
Frequently asked questions
What size should a crochet hat be for an adult?
An average adult head is about 22 inches around. Make the hat 1–2 inches smaller so it stretches to fit, and about 8.5–9 inches tall.
How big should the crown circle be?
Divide the hat circumference by π. For a 20-inch hat, increase until the flat circle is about 6.4 inches across.
My hat is too loose. What happened?
Usually the crown was increased too far or the gauge is looser than expected. Measure the flat circle against the crown diameter in the chart, and try a smaller hook.