Free crochet tool
Crochet Hat Size Calculator
A crochet hat size calculator turns a head circumference into the hat circumference, flat crown diameter and height to work. It applies negative ease so the hat grips, divides the circumference by pi for the crown, and, with your gauge, gives the stitch count for a brim-up hat.
By the crochetpatterns.io editorial team · Reviewed · Editorial policy
Result
How big should a crochet hat be?
A hat should be about 10 % smaller than the head so it stays on. Heights below are measured from crown to brim before folding.
| Size | Head circumference | Hat height |
|---|---|---|
| Preemie | 12–14 | 5 |
| Newborn | 13–15 | 6 |
| 0–3 months | 14–15 | 6.5 |
| 3–6 months | 14–17 | 7 |
| 6–12 months | 16–19 | 7.5 |
| 1–3 years | 18–20 | 8 |
| 3–10 years | 19–20.5 | 8.5 |
| Teen / small adult | 20.5–22 | 9.5 |
| Adult woman | 21–22.5 | 11 |
| Adult man | 22–23.5 | 11.5 |
How do I check a top-down crown?
Work increase rounds until the flat circle measures the crown diameter from the calculator, then stop increasing and work even rounds until the hat reaches the height. Measure across the middle of the circle on a flat surface.
Frequently asked questions
How much negative ease do stretchy hats need?
Ribbed or very stretchy fabric can take 15 % negative ease; stiff stitches need 5 % or less.
How do I measure head circumference?
Wrap a soft tape measure around the forehead just above the eyebrows and ears.
Does a folded brim change height?
Add the fold depth, typically 2–3 inches, to the height.