Circular Knitting Needle Sizes
Circular needles have two parts: the tip diameter (same sizing as straight needles) and the cable length. Getting the length right matters as much as the size.
16" / 40cm: adult hats, sleeves · 24" / 60cm: yokes, shawls · 32" / 80cm: sweaters, blankets · 40" / 100cm+: large blankets, magic loop
Convert Any Needle Size
Open Needle Size Converter →The tip diameter follows the same sizing as straight needles — enter any US, UK, metric, or Japanese size.
Which Cable Length for Which Project
The cable length on a circular needle needs to be shorter than the circumference of what you're knitting — otherwise you can't join the round. As a rule, use a cable that's a few inches shorter than the finished circumference of your project.
| Project | Cable Length | Notes |
|---|---|---|
| Adult hat (body) | 16" / 40cm | Standard for a 20–23" head circumference |
| Hat crown or children's hat | 9" / 23cm or magic loop | Too few stitches for 16" — see note below |
| Sleeves (in the round) | 16" or 12" / 40cm or 30cm | Upper arm width varies; check stitch count |
| Yoke or seamless sweater body | 24"–32" / 60–80cm | Depends on chest size and stitch count |
| Adult sweater body | 32"–40" / 80–100cm | Larger sizes may need 47" / 120cm |
| Shawl or large flat project | 32"–40" / 80–100cm | The longer cable handles more stitches comfortably |
| Blanket or large throw | 40"–60" / 100–150cm | Flat knitting — as long as you need for stitch count |
| Socks (two at once) | 32"–40" / 80–100cm | Magic loop method — long cable, two socks simultaneously |
| Socks (one at once) | 9" / 23cm | Short circular alternative to DPNs |
Tip Diameter — Same as Straight Needles
The diameter of the needle tip is sized exactly like straight needles. A US 8 circular has the same 5.0mm tip as a US 8 straight. The size conversion charts are identical — see US to metric or metric to US for the full charts.
For a quick reference on the most popular circular needle sizes:
The Magic Loop Method
Magic loop lets you knit small circumferences on a long circular needle (usually 40" / 100cm or longer) by pulling a loop of cable out at the midpoint. It's a useful alternative to having multiple lengths — you can knit a hat, socks, or sleeves on the same long circular you use for sweaters.
The technique works best with a flexible cable. Needles with stiffer cables (some older metal circulars) are harder to work with for magic loop because the cable doesn't bend easily enough to form the loop. Modern nylon and coated cables handle it well.
Whether to use magic loop, short circulars, or DPNs for small circumferences comes down to personal preference. All three methods produce the same fabric. See the DPN size guide if you prefer working with double-pointed needles.
Interchangeable Circular Needle Sets
Interchangeable circulars are sets where the needle tips screw or click onto interchangeable cables of different lengths. They're a practical long-term investment — you get multiple sizes and multiple cable lengths without buying individual needles for each combination.
Most sets cover US 4–11 (3.5–8.0mm) in needle size, with cables ranging from 24" to 60". The brands most commonly recommended are Knitter's Pride Karbonz and Royale, Addi Click and Turbo, ChiaoGoo Red Lace, and HiyaHiya Sharp. Each brand's cables and tips are usually not interchangeable with other brands.
If you're buying your first interchangeable set, a mid-range set covering US 4–10 (3.5–6.0mm) with 24", 32", and 40" cables covers the majority of adult garment and accessory patterns.