Yarn Equivalents: US, UK, WPI…

Most of the time I use trial and error to find the correct yarn for a project. If an American pattern states “worsted”, there might be a problem because the UK does not have an exact equivalent. This may mean that the finished item is too small, large, or lack the drape and texture of the intended design. I prefer to use WPI to compare weight or thickness, as it’s more precise and avoids confusion. I have included the recommended knitting needle size for each thickness because that might provide another clue when reading the label.

Advice, as always, is to make a test gauge or swatch to check the item will be the correct size.

WPI – Wraps Per Inch

In the privacy of your own home, measure your fingers (please not toes.. phew!) and find a bit of your body that is easily accessible and is about 1 inch long! Alternatively, every time you go yarn shopping make sure you take a ruler. When shopping, take a ball of yarn and loosely wrap or lay the yarn on your 1 inch thing. The strands should touch without squashing. If it’s in a nice ball, you might be able to use some strands lying next to each other for this. The number of strands that will fit along 1 inch is your WPI (wraps per inch).

Yarn Equivalents
WPI USA UK AUST Knitting (mm)
    cobweb 1 ply  
18 lace lightweight baby 2 ply 1.50 – 2.25
16 sock or light fingering baby 3 ply 2.25 – 3.00
14 fingering 4 ply 4 ply 2.25 – 3.25
12 sport light DK 5 ply 3.25 – 3.75
11 light worsted double knit 8 ply 3.75 – 4.50
9 worsted try aran or thin DK 10 4.50 – 5.50
8 aran aran   4.50 – 5.50
  chunky bulky 16  
7 bulky chunky 20 5.50 – 8.00
6 or 5 super bulky super chunky   8.00 +