Size 7 Crochet Hook (4.5 mm): Yarn Weight, Gauge and Size Conversions

The US 7 hook is 4.5 mm across the shank, about 0.18 inch. Hook size is measured on the shank, the smooth section between the throat and the thumb rest, because that part sets the size of every loop. 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 G-6 (4 mm) and H-8 (5 mm).

CYC places 4.5 mm within the recommended hook range for fine (sport) and light (DK) yarn. Light (DK) is the usual match, with a hook range of 4.5 to 5.5 mm (size 7 to I-9) and a gauge of 12 to 17 single crochet per 4 inches. Sitting where two categories meet, it gives the lighter yarn a looser, drapier fabric and the heavier yarn a firmer one. Amigurumi often uses a smaller hook than the label for tight stitches.

At about 17 single crochet per 4 inches, our estimate for light (DK) yarn on a 4.5 mm hook, a 50 inch wide throw starts with about 214 chains, including 1 turning chain. A 42 inch baby blanket needs about 180 and a 90 inch queen about 384. 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 7. 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 4.5 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 7 knitting needle is also 4.5 mm. Same diameter does not mean same yarn: CYC pairs light (DK) yarn with 4.5 to 5.5 mm (size 7 to I-9) hooks but 3.75 to 4.5 mm (US 5 to 7) needles, because crochet stitches are denser. For the same yarn, crocheters usually reach for a bigger tool than knitters.

For chunky projects, yes. A 4.5 mm hook works up fast: a 50 inch throw starts with only 214 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.

Work a swatch at least 6 inches square in the stitch the pattern names, lay it flat without stretching it, and count the stitches across the center 4 inches. On a 4.5 mm hook in light (DK) yarn that is about 17 single crochet per 4 inches. Gauge is not a formality: the same 214 chain foundation worked 1 stitch per 4 inches tighter measures about 47.3 inches instead of 50, roughly 2.7 inches narrower. Feed your own swatch into the gauge calculator and it converts to a stitch count for any width.

Amigurumi is worked a size or two smaller than the ball band suggests, so the single crochet fabric stays tight enough that the stuffing cannot show through. With worsted weight yarn, whose CYC range is 5.5 to 6.5 mm (I-9 to K-10.5), that usually means something closer to 3.5 to 4.5 mm. A 4.5 mm hook sits inside that band, which is why it turns up in so many amigurumi patterns. Scale a finished piece with the amigurumi size calculator.