Yarn Weight Table
| Category | Common yarn types | Knit gauge (sts / 4 in) | Needle (mm) | US needle |
|---|---|---|---|---|
| 0 | Lace: fingering, 10-count thread | 33 to 40 | 1.5 to 2.25 | 000 to 1 |
| 1 | Super fine: sock, fingering, baby | 27 to 32 | 2.25 to 3.25 | 1 to 3 |
| 2 | Fine: sport, baby | 23 to 26 | 3.25 to 3.75 | 3 to 5 |
| 3 | Light: DK, light worsted | 21 to 24 | 3.75 to 4.5 | 5 to 7 |
| 4 | Medium: worsted, aran, afghan | 16 to 20 | 4.5 to 5.5 | 7 to 9 |
| 5 | Bulky: chunky, craft, rug | 12 to 15 | 5.5 to 8 | 9 to 11 |
| 6 | Super bulky: bulky, roving | 7 to 11 | 8 to 12.75 | 11 to 17 |
| 7 | Jumbo: jumbo roving | 6 or fewer | 12.75 and up | 17 and up |
Yarn weight is not how much your skein weighs - it is the thickness category of the strand, and the industry standard is the Craft Yarn Council system: eight numbered categories from 0 (lace) to 7 (jumbo), printed on the yarn label as a small gauge symbol. The symbol matters less than what surrounds it, because the standard defines each category by gauge - how many stitches you get per 4 inches of knitting - rather than by the strand alone. That is the whole philosophy of the system: two yarns with the same category number can feel noticeably different, but if both give you 18 stitches per 4 inches on the needles the chart recommends, they are interchangeable for pattern purposes.
The chart below is that standard in full: every category with its common yarn names (fingering, DK, worsted, chunky - the words patterns and stores actually use), the knit gauge range, and the needle sizes in both millimeters and US numbers. Two habits make the chart pay off immediately. First, buy yarn by gauge match, not category match: a pattern calling for a category 4 worsted at 18 stitches per 4 inches will forgive a different-brand worsted that hits the same gauge, and will punish a same-category yarn that knits to 15. Second, treat the needle column as the standard starting point, not a rule: your personal tension decides whether you go up or down a size, and the swatch is where that decision gets made - the needle range gets you close, the gauge swatch gets you right.
How to use
- Knit a swatch at least 4 inches square in the yarn and needle you plan to use, wash and dry it the way you will treat the finished piece, then count stitches across the middle 4 inches - that number, not the label symbol, is your yarn weight in practice.
- Read the gauge column: your count should land inside the category range - 16 to 20 stitches per 4 inches is category 4 (medium/worsted); if you are above the range, your fabric is too dense, so go up a needle size; below it, go down.
- To substitute yarns, match the gauge and the needle range, not the category number alone - then check the yardage per gram against the original yarn, because a thicker-feeling worsted and a tight-spun worsted can share a category but not a yardage budget.
Frequently asked questions
Why does the chart define weight by gauge instead of by strand thickness?
Because gauge is the number a pattern actually depends on. Strand thickness in millimeters would seem more direct, but yarn is squishy: two strands of identical diameter can knit up differently depending on ply structure, spin tightness, elasticity and fiber, and the same strand knits to different gauges at different tensions. Stitch count per 4 inches collapses all of that - fiber, ply, spin, and your hands - into one number that directly predicts whether a sweater comes out the size the pattern promises. That is also why the categories span ranges (category 4 covers 16 to 20 stitches) rather than exact diameters: the banding says these yarns behave alike at the recommended needles, not that they measure alike with calipers. The practical consequence for substitutions: a category 3 from one brand may knit closer to category 4 than some category 4s do - the chart gives you the expected neighborhood, your swatch gives you the verdict, and any pattern worth its price tells you its gauge so the two can be compared directly. Crafters who skip the swatch are not skipping a formality; they are gambling the finished measurements on the loosest column of the whole system.
What do the category names mean - is DK a weight or a yarn type?
The names are descriptive traditions that the standard absorbed: fingering, sport, DK (double knitting), worsted, aran, chunky, bulky, roving - each began as a specific yarn construction style and now doubles as a thickness shorthand. In the standard table they map to categories like this: lace (0) covers fingering-weight lace and 10-count crochet thread; super fine (1) is sock, fingering and baby yarn; fine (2) is sport and baby; light (3) is DK and light worsted; medium (4) is worsted, afghan and aran; bulky (5) is chunky, craft and rug yarn; super bulky (6) is bulky and roving; jumbo (7) is the extreme roving end. The mess behind the tidiness: worsted is simultaneously a yarn type (a smooth worsted-spun construction), a weight class (category 4 in the UK-influenced naming) and a specific weight system (worsted count, a spinning fineness measure) - context decides which one a label or pattern means. This is exactly why the standard numbers the categories: the digit is unambiguous where the words are not. When a US pattern says worsted weight and a UK pattern says aran, both usually mean the same 16-to-20-stitch category 4 band, and the gauge column is how you confirm the translation.
How do crochet hooks relate to the needle sizes in this chart?
The same standard covers both crafts with separate sizing columns, and they are not interchangeable. The chart gives the knitting side - metric needle millimeters and US needle numbers - but the standard also assigns crochet hook sizes per category (a B-1 hook for lace up to larger hooks for bulky), because crochet fabric is built from single anchored loops rather than interlocking loops on a held needle, so the same strand needs a different tool diameter to produce a comparable fabric. Two traps worth naming. First, US crochet hook letter-numbers (B-1, E-4, K-10.5) follow a different scale than US knitting needle numbers - a US 8 knitting needle is 5 mm, but there is no US 8 crochet hook; the letter system runs its own way - so always check which craft a chart row describes. Second, crochet gauge is counted differently (stitches per 4 inches, but the fabric behaves differently at the same count), so a crochet pattern and a knitting pattern calling for the same yarn category will still specify different gauge numbers. The unifying habit across both crafts is the same: the swatch, counted over 4 inches, on the tool you will actually use - the chart categories tell you where to start, the gauge tells you where you are.
Can I substitute a yarn from a different category - when does that work?
Only by betraying the category and honoring the gauge. The standard categories are a shared language, not a law of physics: what a pattern needs is a fabric with a specific stitch count per 4 inches and a specific hand (drape, weight, warmth). If a pattern calls for category 3 light at 22 stitches per 4 inches and your category 2 sport yarn hits 22 on needles half a millimeter up, the substitution works - you matched the fabric, not the label. Where substitutions fail is when people match category but not gauge, or gauge but not the fabric character: a tight-spun merino and a lofty alpaca blend can share a gauge and still produce sweaters that weigh and drape completely differently, because fiber elasticity and loft change the fabric beyond stitch count. The disciplined substitution routine: match or deliberately reinterpret the gauge, recalculate yardage (yardage per 100 grams is the comparable number - buy to the original requirement plus 10 percent), knit a real swatch in the round if the piece is knit in the round (purl rows change gauge), and only then commit. One special case: lace and jumbo sit at the edges where gauge bands are widest relative to strand size, so edge-category substitutions are the least forgiving - the closer to category 4 you trade, the safer the swap.