A hat that measures the same as the head slides off. Knit fabric stretches, so beanies are made 5 to 15 percent smaller than the head they are for. That difference is called negative ease.
Picking the ease
- 5% is a relaxed fit for slouchy hats or thick yarn that does not stretch much.
- 10% is the standard fitted beanie. A 22 inch head gets a hat that measures about 19.8 inches around unstretched.
- 15% is snug, good for very stretchy rib or a hat worn under a hood.
The designer rejects a cast-on outside this range and tells the model the stitch counts that would work, so a generated pattern always lands in it.
Length
Length is measured from the brim edge to the top of the crown with the brim unfolded. About 8 to 8.5 inches suits most adults for a beanie worn without a fold; add 2 inches if you want a folded brim. Children's hats run 6.5 to 7.5 inches.
Crown depth
The crown is the part from the first decrease round to the end. Decreasing every round makes a flat, sudden top; spreading the decreases with plain rounds between makes a rounder dome. The designer keeps the crown between 1.25 and 4 inches deep, which covers everything from a flat pillbox top to a soft rounded beanie. A typical crown at 6 rounds per inch is 2 to 3 inches.
Head sizes as a starting point
| Wearer | Head circumference | Hat length |
|---|---|---|
| Baby (6-12 months) | 17-18 in | 6 in |
| Toddler | 18-19 in | 6.5-7 in |
| Child | 19-20.5 in | 7-7.5 in |
| Adult small | 20-21 in | 8 in |
| Adult medium | 21-22.5 in | 8-8.5 in |
| Adult large | 22.5-24 in | 8.5-9 in |
Measure the actual head when you can: a tape around the widest part, just above the ears and eyebrows.