Why a hat should be smaller than the head
It sounds wrong the first time you hear it. A hat knitted to the exact size of the head will slide off, gape at the ears and need constant tugging down. Knitted and crocheted fabric stretches, so hats are deliberately made smaller — usually about 10% — and the stretch does the rest. This is called negative ease, and it is the single most useful thing to know about hat making.
How much depends on the fabric. Springy wool ribbing can take 15% happily. A firm, dense crochet fabric or a bulky yarn with little give does better at 5%, since it simply won't stretch as far. Slouchy hats worn loose at the back need none at all.
Swatch in the body stitch, not the ribbing. Ribbing pulls in dramatically, so measuring gauge over it will give you a stitch count far too high and a hat that ends up enormous. Swatch in whatever stitch the main part of the hat uses.
How long before you start the crown
For a standard adult beanie, work about 7 to 8 inches from the cast-on edge before beginning the crown decreases, which then add another two inches or so. A slouchy hat wants 9 to 10 inches; a close-fitting cap 6½ to 7. If you like to fold the brim up, add the depth of the fold on top of all of that — a two-inch turn-back means two extra inches of knitting.
Working the crown
Crown decreases are usually spread over six or eight points, which is why the calculator can round your cast-on to a multiple of 8 or 12. Divide the stitches into that many equal sections, decrease one stitch in each section every other round at first, then every round as the crown closes, until around 8 to 12 stitches remain. Break the yarn, thread it through the remaining stitches, pull tight and fasten off on the inside.
How much yarn
A DK adult beanie takes around 150 to 200 yards, a child's about 120, and a baby hat well under 100 — which makes hats the ideal home for the single balls left over from bigger projects. Chunky yarn needs fewer yards; fingering considerably more. For a precise figure use the yardage calculator.
Questions we're often asked
How many stitches do I cast on for an adult hat?
It depends entirely on your gauge. At a common 4.5 stitches per inch, an adult woman's hat of about 20¼ inches around needs roughly 92 stitches. Enter your own gauge above rather than borrowing a number from a pattern knitted in a different yarn.
How much smaller than the head should a hat be?
About 10% for most hats. So a 22½ inch head wants a hat measuring around 20¼ inches around. Use 5% for bulky or firm fabric with little stretch, and up to 15% for very springy ribbing.
How do I measure a head?
Run a soft tape measure around the head just above the ears and across the middle of the forehead — the widest part. Keep it snug but not tight. If you're making a surprise gift, measure a hat they already wear and like instead, laid flat and doubled.
How long should a beanie be?
Around 8 inches from cast-on to the start of the crown for a standard adult beanie, with the crown adding roughly 2 inches. Add extra for a folded brim, and work 9 to 10 inches for a slouchy style.
Does this work for crochet hats too?
Yes. Enter your crochet gauge over 4 inches in the stitch you'll use, and the stitch count comes out the same way. Crochet fabric usually stretches less than knitting, so choose 5% ease rather than 10 unless your stitch is particularly loose.