Preemie to adult XL, in inches and centimetres, with the crochet crown diameter
Every hat size from preemie to adult XL, with the head measurement, the finished hat measurement once negative ease is taken off, the height, and the numbers each craft needs: the crown diameter to stop increasing at in crochet, the round loom peg count, and the needle count and row count for a circular knitting machine. Change the ease or switch to centimetres and the whole chart recalculates. Print it and put it in the yarn basket.
The defaults are the standard assumptions. Change any of them and the chart follows.
Head and hat measurements in inches, at 10% negative ease.
| Size | Measurements (in) | Crochet | Loom | Circular machine | ||||
|---|---|---|---|---|---|---|---|---|
| Head | Hat | Height | Crown ø | Sts round | Pegs | Needles | Rows | |
| Preemieunder 5 lb / early | 12.0 | 10.8 | 4.5 | 3.4 | 38 | — | — | — |
| Newborn (0–3 mo)0–3 months | 13.5 | 12.2 | 5.0 | 3.9 | 43 | 24 pegs | — | — |
| Baby 3–6 mo3–6 months | 15.0 | 13.5 | 5.5 | 4.3 | 47 | 24 pegs | — | — |
| Baby 6–12 mo6–12 months | 17.0 | 15.3 | 6.0 | 4.9 | 54 | 31 pegs | 40 needle | 92 |
| Toddler1–3 years | 19.0 | 17.1 | 6.5 | 5.4 | 60 | 31 pegs | 40 needle | 98 |
| Child3–10 years | 20.0 | 18.0 | 7.0 | 5.7 | 63 | 36 pegs | 48 needle | 106 |
| Teen / small adult11+ years | 21.0 | 18.9 | 7.5 | 6.0 | 66 | 36 pegs | 48 needle | 112 |
| Adult Maverage woman | 22.0 | 19.8 | 8.0 | 6.3 | 69 | 36 pegs | 48 needle | 120 |
| Adult Laverage man | 23.0 | 20.7 | 8.5 | 6.6 | 72 | 41 pegs | 48 needle | 126 |
| Adult XLlarge adult | 24.5 | 22.1 | 8.5 | 7.0 | 77 | 41 pegs | 48 needle | 126 |
Head circumference is the only measurement that matters, and it varies by two or three inches inside any age band — especially in babies. If the head is available, measure it. The age column is for when you are making a gift for someone who is not in the room.
Knitted and crocheted fabric stretches. A hat made to the exact head measurement has nothing holding it on and rides up over the course of an afternoon. The fix is negative ease: make the hat 10–15% smaller than the head and let the fabric stretch to grip.
finished hat circumference = head circumference × (1 − ease)
Stretchy fabrics carry more ease than dense ones. Machine-knit stockinette and ribbing are happy at 15%; a tight single crochet fabric is happier at 8–10%. Under 5% the hat creeps up; over about 20% it leaves a mark.
A crochet hat worked top down starts as a flat circle. You increase until the circle is as wide as the hat needs to be around — which is the circumference divided by π — and then you stop increasing and work straight down the sides.
crown diameter = finished hat circumference ÷ π
This one number is why crochet hats come out too big. People keep increasing "until it looks right", and a flat circle that looks right on the table is usually an inch too wide.
Looms and circular machines cannot hit an arbitrary circumference — the peg or needle count fixes it. Those columns pick the standard size whose finished measurement lands closest to the target, and leave a dash when nothing standard fits. That is honest rather than unhelpful: a Sentro 22 makes an 8.5 inch tube and a Sentro 40 makes 15.4 inches, so no circular machine makes a newborn hat, and no chart should pretend otherwise.
Four stitches separate a snug hat from a loose one. That is how tight the tolerance is, and why swatching matters more than the chart does.
About 22 inches (56 cm) for a woman and 23 inches (58.5 cm) for a man. With 10% negative ease that is a finished hat of 19.8 and 20.7 inches. Adult XL runs to 24.5 inches, and adult small or teen down to 21.
A newborn head is about 13.5 inches or 34 cm. The finished hat wants to be about 12 inches around and 5 inches tall, which is a crown diameter of 3.9 inches — stop increasing when the flat circle is not quite 4 inches across.
From 4.5 inches for a preemie to 8.5 inches for an adult L, measured from the centre of the crown to the brim edge. Add 1.5 inches for a slouchy hat and about 2 inches if you want a brim that folds up. The height column here is for a fitted beanie.
The head and hat columns are, because a head is a head. What changes is the stitch and row counts, because gauge differs: knitting and machine knitting produce a stretchier fabric than crochet, so they usually take the higher end of the ease range.
Run a soft tape around the widest part — across the forehead about a finger's width above the eyebrows, and around above the ears. Keep it snug but not tight. If you only have a rigid ruler, use a length of yarn and measure the yarn.