Spinning creates yarn. While yarn takes up less storage space than bulk spinning fibers and is lovely to look at, the point of making it is to use it for something. All of us have purchased lovely fibers and spun them up with no end project in mind because we know we’ll find the perfect use for that yarn someday.

When the perfect pattern comes along, we excitedly dig out our yarn and check the pattern requirements which reads something like: 15 skeins of XYZ Brand yarn, 108yds (99M)/50g; needles size 6 (4mm). Good information, but not enough to tell us if our yarn is going to be suitable for this project. This is where knowing what the standard yarn sizes are can help.

If you’ve purchased any commercial yarns lately you’ve notice the little skein symbol with a number on its ball band on each of your skeins. This is the standard size symbol and the number tells you what size category that yarn falls into. Once you have that information, you can compare your yarn to the standard to figure out if it’s suitable for the project or if you need to adjust needle or hook size or make some pattern adjustments.

Standard yarn classification sizing runs from 0 through 6. Here is the information you need about each size classification:

0 (Zero) - or Lace: Yarns in this category may also be referred to as Fingering weight.
The wpi for singles is 50+ and 35+ for plied yarns.
The ypp for both wool and cotton yarns is 2,500+.
Recommended knitting needles size is 000-1 US or 1.5 –2.25mm.
Knitting gauge is 22 to 40 stitches in 4 inches.
Recommended crochet hook size is Steel 6.7.or 8 or a regular B-1 hook; 1.6-1.4mm.
Recommended Crochet gauge is 32 to 42 double crochets in 4 inches.

1 - or Fingering, Super Fine, or Baby.
The wpi for singles is 25 to 30 and 19 to 22 for plied yarns.
The ypp for wool is 1675 to 2100 yards and 1600 to 2000 for cotton.
Recommended knitting needles size is 1 to 3 US or 2.25 to 3.25mm.
Knitting gauge is 27 to 32 stitches in 4 inches.
Recommended crochet hook size is B-1 to E-4; 2.25 to 3.5mm.
Recommended Crochet gauge is 21 to 32 stitches in 4 inches.

2 - or Fine or Sport weight.
The wpi for singles is 20 to 24 and 15 to 18 for plied yarns.
The ypp for wool is 1350 to 1650 yards and 1350 to 1550 for cotton.
Recommended knitting needles size is 3 to 5 US or 3.25 to 3.75mm.
Knitting gauge is 23 to 26 stitches in 4 inches.
Recommended crochet hook size is E-4 to 7; 3.5 to 4.5mm.
Recommended Crochet gauge is 16 to 20 stitches in 4 inches.
3 - Light Worsted or Double Knitting (DK)
The wpi for singles is 16 to 19 and 12 to 15 for plied yarns.
The ypp for wool is 1100 to 1300 yards and 1000 to 1300 for cotton.
Recommended knitting needles size is 5 to 7 US or 3.75 to 4.5mm.
Knitting gauge is 21 to 24 stitches in 4 inches.
Recommended crochet hook size is 7 to I-9; 4.5 to 5.5mm.
Recommended Crochet gauge is 12 to 17 stitches in 4 inches.

4 - Medium weight, Worsted weight, Afghan, or Aran.
The wpi for singles is 12 to 15 and 9 to 11 for plied yarns.
The ypp for wool is 900 to 1100 yards and 650 to 850 for cotton.
Recommended knitting needles size is 7 to 9 US or 4.5 to 5.5mm.
Knitting gauge is 16 to 20 stitches in 4 inches.
Recommended crochet hook size is I-9 to K-10 1/2; 5.5 to 6.5mm.
Recommended Crochet gauge is 11 to 14 stitches in 4 inches.

5 - Bulky, Heavy Worsted, Chunky, Craft, or Rug weight
The wpi for singles is 9 to 11 and 7 to 8 for plied yarns.
The ypp for wool is 700 to 800 yards and 450 to 600 for cotton.
Recommended knitting needles size is 9 to 11 US or 5.5 to 8mm.
Knitting gauge is 12 to 15 stitches in 4 inches.
Recommended crochet hook size is K-10 1/2 to M-13; 6.5 to 9mm.
Recommended Crochet gauge is 8 to 11 stitches in 4 inches.

6 – Super bulky, Bulky, or Roving
The wpi for singles is 8 or less and 6 or less for plied yarns.
The ypp for wool is 650 or less yards and 400 or less for cotton.
Recommended knitting needles size is 11 and larger US or 8mm or larger.
Knitting gauge is 6 to 11 stitches in 4 inches.
Recommended crochet hook size is M-13 or larger; 9mm or larger.
Recommended Crochet gauge is 5 to 9 stitches in 4 inches.

Abbreviations:
YPP = yards per pound
WPI = wraps per inch