HOW TO Convert Crochet Terms

Knowing how to decipher the terminology used in knitting and crochet between the continents I think is more confusing than learning the craft itself! Having the right weight wool and the right side hook or needle is essential to having a completed item that is the correct size.

The Craft Yarn Council is an excellent resource.

Wool Terms
Here in Australia we usually refer to wool in terms of ply. More recently though, as bamboo, soy and other fibres are being used it the wrapper simply refers to a tension and needle size for reference.

Sock/Baby/Fingering Yarn
This is typically referred to as 4 ply in Australia.
Crochet Tension is 21-28 sts/10cm
Knitting Tension is 26-32 sts/10cm
Crochet Hook Size recommended 2.00 - 3.5mm
Knitting Needle Size recommended 2.00 - 3.25mm

Sport/Baby Yarn
This is typically referred to as 5ply or baby 8 ply in Australia.
Crochet Tension is 16-20 sts/10cm
Knitting Tension is 20-24 sts/10cm
Crochet Hook Size recommended 3.50 - 4.00mm
Knitting Needle Size recommended 3.50 - 4.00mm

Light Worsted/DK
This is typically referred to as 8 ply or Aran in Australia
Crochet Tension is 16-18 sts/10cm
Knitting Tension is 20-24 sts/10cm
Crochet Hook Size recommended 4.00 - 4.50mm
Knitting Needle Size recommended 4.00 - 4.50mm

Worsted Weight Yarn
This is typically referred to as 10-12ply yarn in Australia, by far one of the harder yarns to get in a good range of colours, if you can find it at all!
Crochet Tension is 12-16 sts/10cm
Knitting Tension is 18-20 sts/10cm
Crochet Hook Size recommended 5.00 - 6.00mm
Knitting Needle Size recommended 5.00 - 5.50mm

Bulky/Chunky
This is typically referred to as 12-16 ply, we also call it bulky or chunky yarn, and many of the specialty yarns with boucles and textures would fit into this category.
Crochet Tension is 8-12 sts/10cm
Knitting Tension is 12-18 sts/10cm
Crochet Hook Size recommended 6.50mm +
Knitting Needle Size recommended 5.50 - 8.00mm

It is important to read the instructions carefully.  If a pattern calls for a number 7 steel hook, the metric conversion is 1.7mm, rather than the much larger 4.5mm regular crochet hook. 

Crochet Hook Conversion Chart Metric USA   UK   2.00 mm - 14 2.25 mm 1 / B 13 2.50 mm - 12 2.75 mm C 11 3.00 mm - 11 3.25 mm D 10 3.50 mm 4 / E 9 3.75 mm F - 4.00 mm 6 8 4.25 mm G - 4.50 mm 7 7 5.00 mm 8 / H 6 5.50 mm 9 / I 5 6.00 mm 10 / J 4 6.50 mm 10 1/2 / K 3 7.00 mm - 2 8.00 mm - 0 9.00 mm 15 / N 00 10.00 mm P 000 15.75 mm or 16mm Q -

Steel Hook Chart (thread hooks) Metric USA  UK  .6 mm 14 6 .75 mm 13 - .70 mm 12 5 .8 mm 11 - 1 mm 10 4 1.15 mm 9 - 1.25 mm 8 3 1.50 mm 7 2.5 1.6 mm 6 - 1.7 mm 5 - 1.75 mm 4 2 1.85 mm 3 - 1.95 mm 2 - 2 mm 1 1 2.25 mm 0 00 3 mm 00 -

If in doubt, be sure of the thread size and choose the hook from there.  Size 10 thread is very commonly used in many crochet projects, you will use a 1.50 - 1.75mm hook quite frequently.

Thread Size	Hook Size
100	0.60mm
80	0.60mm
60	0.75mm
40	1.00mm
20	1.25mm
10	1.50mm - 1.75mm
3ply	2.00mm - 2.50mm
4ply	2.50mm - 3.00mm
8ply	3.50mm - 4.00mm