24, 31, 36, 41 and 48 pegs — which loom fits which head, at your gauge
A round loom cannot make an arbitrary size. The pegs are a fixed distance apart, so the peg count and your yarn together decide the finished circumference — and that is the only thing that decides it. This chart maps the five standard looms onto the heads they actually fit, at the gauge you are actually working.
Loom gauge is set by the loom's peg spacing and the yarn. The defaults are a large-gauge loom with two strands of worsted in e-wrap.
At 2.0 stitches per inch — e-wrap, two strands of worsted.
| Loom | Pegs | Finished hat | Fits heads | Hat sizes | Rows |
|---|---|---|---|---|---|
| Small about 5.5" across | 24 | 12.0" | 13.5–15.0" | Newborn (0–3 mo), Baby 3–6 mo | 15–17 |
| Medium about 7.5" across | 31 | 15.5" | 17.0–19.0" | Baby 6–12 mo, Toddler | 18–20 |
| Large about 9.5" across | 36 | 18.0" | 19.0–23.0" | Toddler, Child, Teen / small adult, Adult M, Adult L | 20–26 |
| Extra large about 11.5" across | 41 | 20.5" | 22.0–24.5" | Adult M, Adult L, Adult XL | 24–26 |
| Extra large (48-peg) about 13" across | 48 | 24.0" | — | nothing standard at this gauge | — |
Every round loom in the classic set — the blue, red, green and yellow ones sold in a four-pack, and their equivalents from Boye, Knifty Knitter, Darice and everyone else — has the same peg spacing. Only the number of pegs, and so the diameter, changes. That gives you:
finished hat circumference = peg count ÷ stitches per inch
Two strands of worsted in e-wrap on a large-gauge loom works out at about 2 stitches per inch, which is where the familiar chart comes from: 24 pegs is a 12 inch hat, 31 pegs is 15.5 inches, 36 pegs is 18 inches, 41 pegs is 20.5 inches. Change the yarn and every one of those numbers moves, which is why the chart above is a calculation rather than a picture.
A hat wants negative ease — to be smaller than the head so the fabric stretches to grip it. Loom fabric, especially e-wrap, is very stretchy, so it carries more ease than crochet does: anywhere from 4% to about 22%, with 15% as the comfortable target. That range is wide enough that one loom covers two or three head sizes, and narrow enough that the wrong loom is genuinely the wrong loom. Under 4% the hat slides off; over 22% it leaves a mark and the stitches splay.
Row height on a loom runs about 1.5 times the stitch gauge in e-wrap and about 1.6 times in u-stitch, so:
rows = hat height × stitches per inch × 1.5
Knit to the row count, then take every loop off onto a long tail with a yarn needle, pull tight, and knot inside. A loom hat is gathered, not decreased.
E-wrap (twisted stockinette) wraps all the way round the peg and is the loose, fast, stretchy default. U-stitch wraps flat across the front, making a denser fabric with roughly 15% more stitches per inch — so the same loom in u-stitch gives a hat about 15% smaller. If a loom is a size too big for the head, switching to u-stitch is often the whole fix.
The same arithmetic applies, with one difference: on a long loom or a board you choose how many pegs to work over, so you can hit any circumference you like. Divide the target circumference by your stitches per inch and use that many pegs. Working in the round on a long loom means going up one side and back down the other.
Switch to one strand of worsted on a small-gauge loom (2.5 sts/in) and the same 36-peg loom becomes a 14.4 inch hat, which fits a toddler. The loom did not change; the yarn did.
The 36-peg (about 9.5 inch) loom, with two strands of worsted in e-wrap. That gives an 18 inch hat, which is 18% negative ease on a 22 inch head. Go up to the 41-peg loom for a large adult head, a slouchy fit, or if you are working in u-stitch.
The 24-peg small loom for newborn and 0–6 months, and the 31-peg medium loom for 6–12 months and toddlers — both with two strands of worsted. For a preemie you need a smaller gauge rather than a smaller loom: one strand of worsted on the 24-peg loom.
Hat height times your stitch gauge times 1.5. For an adult hat at 2 stitches per inch that is 8 × 2 × 1.5 = 24 rows; for a newborn, 5 × 2 × 1.5 = 15 rows. Add about 2 inches worth of rows if you want a brim that folds up.
About 9.5 inches across the loom itself, but that is not the hat size. The hat comes out at 36 divided by your stitches per inch — 18 inches with two strands of worsted, or 14.4 inches with one strand on a small-gauge loom. The loom diameter and the hat circumference are different numbers and confusing them is the usual reason a loom hat comes out wrong.
E-wrap wraps all the way around each peg, making a loose, stretchy, fast fabric — the default for hats. U-stitch wraps flat across the front of the peg, making a denser fabric with about 15% more stitches per inch, so the same loom produces a hat roughly 15% smaller.
Yes, and it is more flexible: you choose how many pegs to work over, so you can hit any circumference. Divide your target hat circumference by your stitches per inch to get the peg count, then work in the round by going up one side of the loom and back down the other.