Choosing the right yarn and substituting yarns for use in patterns can be confusing for all of us, particularly when substituting US and European yarns as they all use different names on the yarn labels. This Yarn Weight Chart compares global, number system, UK and US yarn weight categories to aid in choosing substitute yarn for your knitting project.
Tension is measured as the number of stitches and rows per 10cm/4inches.
Yarn plies are confusing as they can be quite different. Soft and fluffy or very tightly wound.
Please note that the chart is a guide, there are times when you will find a yarn that breaks the guidelines. For example, some sock yarns are closer to fingering weight than 4 ply.