Hat Size Calculator

Measure the head circumference, subtract about 10% for negative ease, and multiply by your stitches per inch. Example: a 22-inch head at 10% ease is 19.8 inches; at a worsted gauge of 19 stitches per 4 inches (4.75 per inch) that is 19.8 x 4.75 = 94 stitches, rounded to 96 for a 2x2 rib multiple. The calculator above does this in one step, including the rib-multiple rounding.

About 10% of the head circumference is the standard starting point, roughly 2 to 2.5 inches on an adult head. Use 10-15% for a snug fitted beanie and about 5% for a slouchy hat. More ease than 15% can feel tight and give a headache; zero or positive ease makes the hat slide around.

Both start from the same cast-on math, but a slouchy hat uses slightly less negative ease (around 5%) and is knit about 2.5 inches longer before the crown decreases begin, so the extra fabric pools at the back. A fitted beanie uses 10-15% negative ease and the standard crown-to-brim height from the size chart. Switch the mode above to see both versions calculated side by side.

Divide the stitches into equal sections (8 sections for 56+ stitches, 6 for 36-55, 4 for smaller), then work one decrease round per section count: [k10, k2tog] repeated 8 times takes 96 stitches to 88, then [k9, k2tog] to 80, and so on down to [k2tog] 8 times for 8 stitches. Cut the yarn and thread it through the remaining stitches. The crown planner above prints the full round-by-round schedule for your exact stitch count.

Measure or look up the head size first: a 3-6 month baby is about 16-17 inches around. At a DK gauge of 22 stitches per 4 inches (5.5 per inch) with 10% negative ease, 16.5 x 0.9 x 5.5 = 82 stitches, rounded to an even number for ribbing. Newborns need roughly 70-76 stitches at the same gauge. Pick the size preset above to fill in the standard head measurement automatically.

Measure from the crown of the head to the bottom of the earlobe, or use the standard chart: preemie about 5.5 inches, newborn 6.25, toddler 7.75, child 8.25, adult medium 9.25, adult large 9.75. That measurement covers the whole hat from cast-on edge to the top of the crown; the brim or cuff is part of it, not extra.

A single-layer brim is usually 1.5 to 2.5 inches deep; a folded cuff is 3 to 4 inches so the fold sits at about 1.5 to 2 inches. Convert depth to rows with your row gauge: 2.5 inches at 26 rows per 4 inches is 16 rows (32 for a folded cuff). The brim calculator above also rounds the stitch count to your rib multiple.

1x1 rib needs an even number of stitches (multiple of 2), 2x2 rib needs a multiple of 4, and 3x3 rib a multiple of 6. If your cast-on math gives 94 stitches and you want 2x2 rib, round to 92 or 96. The calculator rounds to your chosen multiple automatically so the ribbing pattern always works out.

Yes. The cast-on math is identical; add 2 selvedge stitches for the seam and work the crown decreases the same way, then seam the back. Hats knit in the round are seamless and slightly stretchier at the join, but a flat-knit hat fits the same head the same way.

One adult hat in worsted weight takes roughly 180 yards, so a single 220-yard skein is enough with margin. Bulky yarn needs fewer yards (about 135 for an adult) and fingering needs more (about 240). Baby and child hats take roughly half to three-quarters of the adult amount. The estimates are built into the size chart above; always buy one extra skein if you are between sizes.

Wrap a soft tape measure around the head at the widest point, across the forehead and just above the ears, keeping it snug but not tight. Typical adult heads measure 21 to 23 inches (53 to 58 cm); measure twice and use the larger number. Measuring the actual head beats guessing from age alone, especially for babies.

Ignore the chart and use your own measured gauge: count stitches over 4 inches of your blocked swatch and enter that number. That is exactly what this calculator is for - static charts only cover two or three standard gauges, while your swatch divided by inches works at any tension, any yarn, any needle size.

Static charts give one cast-on number per size at one fixed gauge, and they never show the crown decrease schedule. A calculator takes your actual head measurement and your actual gauge, rounds to your rib multiple, adds slouchy or fitted length, and prints the full round-by-round decrease plan - the four things charts leave you to figure out by hand.

Bulky yarn at 15 stitches per 4 inches (3.75 per inch) on a 22-inch adult head with 10% negative ease gives 19.8 x 3.75 = 74 stitches, rounded to 72 or 76 for a 2x2 rib multiple. Chunky super-bulky at 10 stitches per 4 inches gives about 50 stitches for the same head. Thicker yarn means dramatically fewer stitches, which is why one chart cannot cover all yarn weights.

No. Cast-on, ease, and decrease math are identical; only the stitch distribution changes. Divide the total as evenly as possible across needles - for example 96 stitches on 4 DPNs is 24 per needle, and magic loop is 48 and 48. Place a marker at the start of the round so the decrease schedule stays aligned.

Yes. Every calculation runs entirely in your browser with JavaScript; nothing you type is sent to any server, stored anywhere, or tracked. The page works offline once loaded, and there is no account, no sign-up, and no analytics on your inputs.