DK and Sport Weight Yarns

DK weight yarns 
20-24 stitches per 10cm/4 inches
with 3.75mm-4.5mm / US5-7
11 wpi
8ply
Yarn Standard #3
.
Sport weight yarns 
24-26 stitches per 10cm/4 inches
with 3.25mm-3.75mm / US2-5
12 wpi
5ply
Yarn Standard #2
.
There is some variation between yarns within the same yarn weight category. To find the right yarn to suit your project: look up the recommended yarn for your pattern and compare that yarn's gauge to the gauge of the yarn you would like to use.