Hat Size Calculator

Knit & crochet

Pick a size or enter a head measurement, add your gauge, and get the cast on, rounds and crochet crown size.

Quick answer. An adult woman's hat for a 22.5 in head, with 2 in of negative ease at 20 stitches per 4 in, needs a cast on of 104 stitches and is about 11 in tall.

Source: Knit Picks Hat Size Guide for sizes and the ease method; cast on rounded to a multiple of 8.

Your hat

1. Who it is for

Size

Head circumference

Hat height

Measured? Pick I measured the head and enter it, with the height you want. Measure around the forehead, just above the ears.

2. Fit and gauge

Negative ease

Stitches per 4 in (10 cm)

sts

Rows or rounds per 4 in (10 cm)

rows

2 in (5 cm) of negative ease gives a snug beanie. Use 1 in for less stretchy fabric, 0 for a loose fit.

Result

Your hat

Knit: work 8 evenly placed decreases about every other round once you are a little short of the height.

Hat size chart

Head circumference and finished hat height by age, with a folded brim or a little slouch, and the worsted yarn each takes.

Hat sizes from preemie to adult
Size	Head	Hat height	Worsted yarn
Preemie, 1 to 2 lb	9 in (22.9 cm)	3.5 in (8.9 cm)	50 to 110 yd
Preemie, 3 to 4 lb	11 in (27.9 cm)	4 in (10.2 cm)	50 to 110 yd
Preemie, 4 to 5 lb	12 in (30.5 cm)	4.5 in (11.4 cm)	50 to 110 yd
Preemie, 5.5 to 6 lb	13 in (33 cm)	5 in (12.7 cm)	50 to 110 yd
Newborn	14 in (35.6 cm)	6 in (15.2 cm)	100 to 150 yd
Baby, 3 to 6 months	17 in (43.2 cm)	7 in (17.8 cm)	100 to 150 yd
Baby, 6 to 12 months	18 in (45.7 cm)	7.5 in (19.1 cm)	100 to 150 yd
Toddler, 1 to 3 years	19 in (48.3 cm)	8 in (20.3 cm)	100 to 150 yd
Child, 3 to 10 years	20 in (50.8 cm)	8.5 in (21.6 cm)	100 to 180 yd
Pre-teen and teen	21 in (53.3 cm)	10 in (25.4 cm)	100 to 180 yd
Adult woman	22.5 in (57.2 cm)	11 in (27.9 cm)	120 to 200 yd
Adult man	24 in (61 cm)	11.5 in (29.2 cm)	170 to 250 yd

Sizes and yardage from Knit Picks. The Craft Yarn Council gives head ranges of 21 to 23 in for women and 22 to 24 in for men.

Cast on by gauge

With 2 in of negative ease, rounded to a multiple of 8.

Hat cast on by size and gauge
Size	14 sts / 4 in	18 sts / 4 in	20 sts / 4 in	24 sts / 4 in	28 sts / 4 in
Newborn	40	56	64	72	88
Baby, 3 to 6 months	56	64	72	88	104
Baby, 6 to 12 months	56	72	80	96	112
Toddler, 1 to 3 years	56	80	88	104	120
Child, 3 to 10 years	64	80	88	112	128
Pre-teen and teen	64	88	96	112	136
Adult woman	72	96	104	120	144
Adult man	80	96	112	136	152

How the hat maths works

Hat circumference = head circumference minus negative ease
Cast on = hat circumference x stitches per inch, rounded to a multiple of 8
Rounds = height x rounds per inch
Crochet crown circle = hat circumference / 3.14

Knit until the hat is a little short of the height, then work 8 evenly placed decreases about every other round to close the crown.

Sources

Knit Picks, Hat Size Guide: head sizes, hat heights, worsted yardage and the negative ease method. https://www.knitpicks.com/learning-center/hat-size-chart
Craft Yarn Council, Head Circumference Chart: adult head ranges. https://www.craftyarncouncil.com/standards/head-circumference-chart

Common questions

How many stitches do I cast on for an adult hat?

For a 22.5 in head with 2 in of negative ease at 20 stitches per 4 in, cast on 104. At a bulky 14 stitches per 4 in it is 72.

What size is a newborn hat?

A newborn head is about 14 in (35.6 cm) around, and the hat about 6 in tall, so make the hat about 12 in around for a snug fit.

What is negative ease in a hat?

The hat is smaller than the head so it stretches and stays on. 2 in (5 cm) is most common for a snug beanie with a folded brim.

How tall should a hat be?

About 11 in for an adult woman and 11.5 in for an adult man, including a folded brim or a little slouch. Fitted hats are shorter.

How wide should the crown circle be for a crochet hat?

Divide the hat circumference by 3.14. A 20.5 in hat needs a flat crown circle about 6.5 in across before you stop increasing.

How much yarn do I need for a hat?

In worsted weight, about 120 to 200 yd for an adult woman and 170 to 250 yd for an adult man.