Yarn Weight Conversion Chart: The Complete CYC 0-7 Reference Guide

Understanding the CYC yarn weight system

The Craft Yarn Council Standard Yarn Weight System standardised yarn classification in the early 2000s. Before this, "worsted" in the US, "10-ply" in Australia, and "Aran" in Britain could all describe roughly the same thickness — or three slightly different yarns, depending on the manufacturer. The CYC numbers 0-7 (with each yarn label also showing a small numbered yarn-ball icon) cut through that confusion. A label showing "4" is worsted-weight in any country, by any manufacturer.

The numbered system did not replace traditional names — most patterns still call for "DK weight" or "fingering" — but the CYC number provides an unambiguous reference. When a pattern's stated weight name confuses you, find the CYC number on the yarn label and match it. The number is the truth; the name is descriptive.

Complete yarn weight conversion chart (CYC 0-7)

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For the corresponding crochet hook size chart in metric, US, and UK conventions, see the dedicated reference article.

Each yarn weight in detail

CYC #0 — Lace

The thinnest commercial yarn. Used almost exclusively for traditional doilies, fine lace shawls, and thread crochet. Worked with very small hooks — the Craft Yarn Council lists 1.4–1.6 mm in steel, or 2.25 mm in a regular hook. Steel hooks are numbered in reverse, so a higher steel number is a smaller hook. Cotton in lace weight produces stiff structural lace; wool/silk blends produce drapey shawls. Most modern crocheters never use lace weight; it is a specialist material.

CYC #1 — Fingering / Sock

The standard yarn for socks. Fine enough that finished socks fit comfortably inside shoes. Also used for lacy garments where drape matters. Brands: Patons Kroy Socks, Knit Picks Stroll, Drops Fabel.

CYC #2 — Sport / Baby

Slightly thicker than fingering. Common for baby garments and light summer wearables. Used to be more popular than it is today; many baby patterns have shifted to DK (#3) for slightly faster work-up.

CYC #3 — DK (Double Knitting) / Light Worsted

The "Goldilocks zone" for many crocheters — fine enough for garments with drape, thick enough to work up quickly. DK is the standard for many cardigans, sweaters, and lightweight blankets. Brands: Stylecraft Special DK, Drops Cotton Merino.

CYC #4 — Worsted / Aran

The most popular yarn weight in North America. Used for afghans, hats, mittens, amigurumi, and most general projects. Brands: Red Heart Super Saver, Caron Simply Soft, Bernat Super Value.

CYC #5 — Bulky / Chunky

About 1.4 times the diameter of worsted, which is roughly twice the cross-section — the published WPI midpoints are 10.5 for worsted against 7.5 for bulky. Fewer, larger stitches cover the same area, so the same project finishes appreciably faster. Bulky blankets are warm and finish fast. Brands: Lion Brand Hometown USA, Bernat Softee Chunky.

CYC #6 — Super Bulky

Statement-piece yarn. Chunky throws, oversized scarves, dramatic winter accessories. Works up very fast, because each stitch covers far more ground than a worsted stitch does.

CYC #7 — Jumbo

Roving-style yarn (often un-spun fleece). Used for arm-knitting/crocheting, where the "hook" is your arm. Trendy but specialist. One skein typically completes a small throw.

Yards per 100 g is not fixed by the CYC number. It falls out of thickness and fibre density together, so the category tells you how thick a yarn is, not how far a ball will go. Red Heart Super Saver (#4) is 364 yd per 198 g and Caron Simply Soft (#4) is 315 yd per 170 g — both land near 185 yd per 100 g. Stylecraft Special DK (#3) is 322 yd per 100 g, close to double the yardage just one category thinner. Read the yardage off the ball band in front of you and put that figure into a yardage calculation; the weight category will not supply it.

WPI (wraps per inch) — measuring thickness without a label

Measured an unknown yarn? Enter your reading in the WPI calculator and it reports every Craft Yarn Council weight range the measurement falls inside — which is often more than one.

WPI measures how many strands of yarn wrap around a 1-inch ruler without overlapping or gapping. It is the most reliable way to verify a yarn's actual weight when the label is missing or you have unlabelled stash yarn. The full measuring method covers wrapping tension, how many readings to take and what to do with haloed or elastic yarns. Wrap the yarn around a ruler with neutral tension (no stretching, no compressing) for one inch, count the wraps, and compare to the chart above. WPI measures thickness directly rather than reading it off a label, which is what makes it useful for unlabelled stash yarn. It is not exact: the Craft Yarn Council notes that the result varies with how tightly you wrap, and a soft woollen-spun yarn compresses under the wrap in a way a firm cotton does not. The published ranges also overlap, and not just in pairs: a reading of 12 wraps sits in Fine (12–18), Light (11–15) and Medium (9–12) at once. Treat WPI as a way to narrow the field, then confirm with a gauge swatch.

To do the WPI test accurately: hold the ruler horizontally, wrap the yarn around it perpendicular to the long edge, count between two pin marks exactly 1 inch apart, repeat 3 times across the skein, and average the results. A 10-wrap yarn falls in the #4 medium range and a 7-wrap yarn in the #5 bulky range. A 12-wrap yarn is genuinely ambiguous — it sits inside #2 fine (12–18), #3 light (11–15) and #4 medium (9–12) simultaneously — which is exactly when a swatch decides it rather than the ruler.

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International yarn weight names

The same physical yarn weight goes by different names in different countries. The CYC number on the label is the same everywhere; the descriptive names are not.

Weight category and wraps per inch both describe the yarn on its own. What decides a finished size is the fabric you make from it, which is why the last step of any conversion is measuring gauge in the yarn you actually intend to use rather than trusting the category.

Doubling up — combining yarn weights

Two strands of finer yarn held together can substitute for a thicker single strand. The usual approximations: two strands of CYC #1 fingering ≈ one strand of CYC #3 DK; two strands of CYC #3 DK ≈ one strand of CYC #4 worsted or #5 bulky; three strands of CYC #1 ≈ one strand of CYC #4 worsted. These follow from cross-sections adding rather than diameters, so holding n strands together multiplies thickness by roughly √n and divides WPI by the same factor. They cannot be sharper than that, because the CYC bands they map between overlap and vary hugely in width — Super Fine covers 14–30 WPI on its own. Always swatch the doubled combination before committing; actual behaviour also depends on the specific yarns' compressibility and twist.

Held-double crochet is common for adding contrasting colour without changing pattern (one strand of base colour, one strand of accent — produces a marled effect), for using up small leftover skeins, and for shifting a pattern's weight category without changing yarn.

Sources & further reading

• Craft Yarn Council — Standard Yarn Weight System — the categories 0–7, gauge ranges and hook ranges reproduced in the chart above.
• Craft Yarn Council — How to measure wraps per inch — the WPI method and the published WPI ranges.
• Craft Yarn Council — Standards FAQs — on how the categories are intended to be used.
• Ravelry — yarn weight system reference

The Craft Yarn Council classifies yarn by thickness; it does not certify that two yarns in a category are interchangeable. Category 0 gauge is published in double crochet while every other row is single crochet, which is why the lace row is marked separately. Category 0 is also the only row where the Council lists two hook entries rather than a range — steel 1.4–1.6 mm, or a 2.25 mm regular hook. WPI ranges overlap by design and vary with wrapping tension.