G-6 Crochet Hook (4 mm): Yarn Weight, Gauge and Size Conversions

The G-6 hook is 4 mm across the shank, about 0.16 inch. Charts also list 4.25 mm (G), covered on this page. Letters and numbers vary between brands, especially at the large end, so the millimeter size stamped on the hook is the one to trust. The neighboring sizes are F-5 (3.75 mm) and US 7 (4.5 mm).

CYC places 4 mm within the recommended hook range for fine (sport) yarn. Fine (sport) is the usual match, with a hook range of 3.5 to 4.5 mm (E-4 to size 7) and a gauge of 16 to 20 single crochet per 4 inches. It sits inside one category, so it is a straightforward match. Amigurumi often uses a smaller hook than the label for tight stitches.

At about 18 single crochet per 4 inches, our estimate for fine (sport) yarn on a 4 mm hook, a 50 inch wide throw starts with about 226 chains, including 1 turning chain. A 42 inch baby blanket needs about 190 and a 90 inch queen about 406. Foundation chains tend to be tighter than the rows above, so many crocheters chain with a hook one size larger.

The old UK size is 8. Old UK numbers run in reverse, so higher numbers are finer hooks. Current UK and European patterns use millimeters, so a pattern asking for a 4 mm hook means this exact size. Watch the stitch names as well as the hook: UK double crochet is the same stitch as US single crochet, and UK treble is US double crochet.

A US 6 knitting needle is also 4 mm. Same diameter does not mean same yarn: CYC pairs fine (sport) yarn with 3.5 to 4.5 mm (E-4 to size 7) hooks but 3.25 to 3.75 mm (US 3 to 5) needles, because crochet stitches are denser. For the same yarn, crocheters usually reach for a bigger tool than knitters.

For chunky projects, yes. A 4 mm hook works up fast: a 50 inch throw starts with only 226 chains, and stitches are easy to see. The catch is weight: bulky yarn and a big blanket in your lap get heavy, and large loops can be hard to read. A scarf or cowl makes a good first project at this size.