Knitting Needle Size Chart

Knitting patterns specify needle size in one of three systems: US numbers, metric millimeters, or the old UK/Canadian numbered system. Metric millimeters are the universal reference — a 5.0 mm needle is 5.0 mm everywhere, regardless of what US or UK number it carries.

How it works

The table maps all three systems across the full range of standard sizes:

• Metric (mm) — the actual shaft diameter; the universal standard
• US number — the American designation, increasing with size but not proportional to mm
• Old UK/Canadian number — runs opposite to US (higher number = smaller needle)

Practical examples

Example 1 — Pattern says US 8. Look up US 8 in the table: it corresponds to 5.0 mm. Purchase or confirm your needle is 5.0 mm for an accurate gauge swatch.

Example 2 — UK pattern calls for size 8. In the old UK system, size 8 = 4.0 mm (US 6). Not US 8 — the systems run in opposite directions.

Example 3 — Your gauge is too tight. You are getting 22 stitches per 4 inches and need 20. Move up one needle size: if you were on 4.5 mm (US 7), try 5.0 mm (US 8).

Common mistakes

• Assuming US 8 = UK 8. They are not the same — US 8 = 5.0 mm; UK 8 = 4.0 mm.
• Not measuring your needle. Brand tolerances vary slightly. Always measure with a needle gauge before a gauge-sensitive project.
• Ignoring needle length and material. Circular vs. straight and metal vs. bamboo can affect tension for some knitters, independent of the size number.

International and regional variations

Quick reference

For a side-by-side view of all knitting needle sizes, crochet hook sizes, and yarn weight recommendations in one page, see the Knitting Needle & Crochet Hook Size Chart →.