US Size 9 Knitting Needles (5.5 mm): Yarn Weight, Gauge and Conversions
A US size 9 knitting needle is 5.5 mm in diameter, old UK and Canadian size 5. It suits medium (worsted) and bulky (chunky) yarn, and bulky (chunky) knits at 12 to 15 stitches per 4 inches. At about 15 stitches per 4 inches, a 20 inch hat needs about 76 stitches and an 8 inch scarf about 30.
Knitting needle size is the diameter of the shaft, measured in millimeters. This needle is 5.5 mm, about 0.22 inch across. US size 9 is the American label for a 5.5 mm needle, and old UK and Canadian size 5 is the same needle. The millimeter figure is the one that matches across every brand, so it is printed on most needles and needle gauges.
What is a US 9 knitting needle in mm and old UK sizes?
| Metric | 5.5 mm |
|---|---|
| Inches (diameter) | 0.22 in |
| US size | 9 |
| Old UK and Canadian size | 5 |
| Crochet hook, same diameter | I-9 (5.5 mm) |
| Usual yarn weight | bulky (chunky) |
| Estimated gauge | about 15 stitches per 4 in |
Some charts also list the sizes below. They are close enough to 5.5 mm that they share this page.
| Metric | US | Old UK | Note |
|---|---|---|---|
| 5.25 mm | 9 | None | Less common; listed on the CYC chart. |
What yarn weight goes with US 9 needles?
The Craft Yarn Council lists 5.5 mm inside the recommended needle range for the yarn weights below. The hat and scarf columns show how many stitches the full gauge range of each weight gives, so you can see how much the yarn choice moves the numbers.
| Yarn weight | CYC needle range | Gauge per 4 in | 20 in hat | 8 in scarf |
|---|---|---|---|---|
| Medium (worsted) | 4.5 to 5.5 mm (US 7 to 9) | 16 to 20 | 80 to 100 | 32 to 40 |
| Bulky (chunky) | 5.5 to 8 mm (US 9 to 11) | 12 to 15 | 60 to 76 | 24 to 30 |
How many stitches do you cast on with US 9 needles?
The estimated gauge places 5.5 mm within the CYC range for bulky (chunky) yarn: the smallest recommended needle gets the most stitches per 4 inches and the largest gets the fewest. That gives about 15 stitches per 4 inches on this needle. Circular pieces are rounded to a multiple of 4 so 2x2 ribbing works out.
| Piece | Width or circumference | Cast on (estimate) |
|---|---|---|
| Hat, 20 in around (multiple of 4) | 20 in | about 76 |
| Snug hat, 18 in around | 18 in | about 68 |
| Cowl, 24 in around | 24 in | about 92 |
| Scarf, 8 in wide | 8 in | about 30 |
| Baby blanket, 42 in wide | 42 in | about 158 |
| Throw, 50 in wide | 50 in | about 188 |
Swatch before you trust any cast-on number
Knit a swatch at least 6 inches wide, wash and dry it the way you will treat the finished piece, then count stitches across the center 4 inches. Put your real number into the cast-on calculator for an exact count.
Needles and supplies for US 9 (5.5 mm)
ChiaoGoo Red Lace Stainless Steel Circular Needle, 32 inch, US 9
$22.87A 32 inch stainless steel US 9 (5.5 mm) circular for sweaters and blankets.
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Lion Brand Vanna's Choice Yarn, Medium Worsted #4, 3 Pack, Barley
$18.82Three 170 yard skeins of worsted acrylic with a published knit gauge on US 9 needles.
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Knit Picks Sunstruck Wood Interchangeable Needle Set, US 4 to 11
$77.47Nine pairs of birch tips from US 4 to 11 (3.5 to 8 mm) with four cables, the budget way to own every mid size.
Check pricePrices change often, so confirm on Amazon. As an Amazon Associate we earn from qualifying purchases.
What crochet hook matches a US 9 knitting needle?
The I-9 crochet hook is also 5.5 mm. Diameter is where the match ends, though: crochet fabric is denser, so CYC pairs bulky (chunky) yarn with 5.5 to 8 mm (US 9 to 11) needles but larger hooks. A 5.5 mm hook usually suits a lighter yarn than a 5.5 mm needle does.
What are the knitting needle sizes next to US 9?
Frequently asked questions
What size is a US 9 knitting needle in mm?
A US size 9 needle is 5.5 mm in diameter, about 0.22 inch. The old UK and Canadian size is 5. Charts also list 5.25 mm (US 9), covered on this page. US numbers were never fully standardized, so trust the millimeter size printed on the needle or check it in a needle gauge. The neighboring sizes are US 8 (5 mm) and US 10 (6 mm).
What yarn weight do you use with US size 9 needles?
CYC places 5.5 mm inside the recommended needle range for medium (worsted) and bulky (chunky) yarn. Bulky (chunky) is the usual match: its range is 5.5 to 8 mm (US 9 to 11), knitting at 12 to 15 stitches per 4 inches. Because 5.5 mm sits where two categories meet, it makes the lighter yarn slightly loose and the heavier yarn slightly firm. Your pattern gauge matters more than the category name.
How many stitches do I cast on for a hat with US 9 needles?
At about 15 stitches per 4 inches, our estimate for bulky (chunky) yarn on 5.5 mm needles, a 20 inch hat needs about 76 stitches, rounded to a multiple of 4 for ribbing. For a snug fit many patterns size the hat 1 to 2 inches smaller than the head, which is about 68 stitches at 18 inches. The estimate places the needle within the CYC gauge range, so knit a swatch and recount before you cast on.
How many stitches for a scarf on US 9 needles?
Cast on about 30 stitches for an 8 inch wide scarf at 15 stitches per 4 inches. A 6 inch scarf needs about 23 and a 10 inch scarf about 38. Stitch pattern changes both width and yarn: garter stitch used about 46 percent more yarn than stockinette in one test. A quick 4 inch swatch in the stitch you plan to use gives a better count than the label gauge.
What crochet hook is the same size as a US 9 knitting needle?
The I-9 crochet hook is also 5.5 mm, so the two share a diameter. They are not interchangeable for the same yarn, though. CYC pairs bulky (chunky) yarn with 5.5 to 8 mm (US 9 to 11) needles but 6.5 to 9 mm (K-10.5 to M-13) hooks, because crochet fabric is denser. A 5.5 mm hook usually suits a lighter yarn than a 5.5 mm needle does.
Are US size 9 needles good for beginners?
Yes. 5.5 mm needles with bulky (chunky) yarn make stitches large enough to see and count, and a 20 inch hat is only about 76 stitches around, so projects grow quickly. Smooth, light-colored yarn makes mistakes easier to spot. If your hands ache, square or triangular ergonomic needles in this size are worth trying.
How we research: we compare manufacturer specifications, owner manuals, published standards and recurring themes in verified owner reviews. We do not test products in person, and this is researched guidance, not professional advice. Follow your machine manual and pattern, and take care with rotary cutters, hot irons and needles. As an Amazon Associate we earn from qualifying purchases.