The weight of the yarn is essentially the thickness of the yarn.  Different weights of yarn will deliver different stitch gauges when knit or crocheted.  It is important to select the correct weight for the pattern you are knitting or crocheting, as well as the correct needle size to achieve the gauge specified in the pattern.  The weight of a yarn is measured in stitches per inch.  This is simply the number of stitches that span a specific measurement.  The weights below are guides to help narrow your search, but all weights within a category may not be the same as each category has a range that it covers.  The numerical gauge on a yarn should match your pattern & a gauge swatch should be done before knitting or crocheting to deliver the best results.  Always remember to block your gauge swatch.

The weight categories below are based on standards written by The Craft Yarn Council.