What weight is my yarn?

If the label's gone, or it says something unhelpful like "medium" or a brand's own name for a thickness, wraps per inch will tell you where it sits on the standard 0–7 scale.

The WPI method

1. Take a ruler, or a pencil with an inch marked on it.
2. Wrap the yarn around it, side by side, touching but not overlapping, without pulling it tight — as it would sit in fabric.
3. Count the wraps in one inch. Do it twice and take the average.

Reading the number

Where it goes wrong

• Pulling tight compresses the yarn, gives too many wraps, and makes it look thinner than it is. Wrap as loosely as the yarn will sit.
• Fuzzy or halo yarns (mohair, brushed alpaca): the halo inflates the count. Wrap, then look at the core strand.
• Bouclé, thick-and-thin, chainette: wrap three inches and divide by three, to average out the lumps.
• Borderline results — 10 wpi could be DK or worsted — do the gauge check.

The gauge check

Knit a small swatch on the needle the table suggests and count stitches across four inches. Compare with the gauge column on Gauge. Around 21–24 stitches is DK territory; 16–20 is worsted. Gauge is what the pattern actually cares about, so when WPI is ambiguous, gauge wins.

"Weight" vs weight

The category ("worsted weight") and the grams on a scale are unrelated. A 100 g ball of lace weight holds around 800 yards; a 100 g ball of super bulky, around 70. See Yarn weights for the full chart.

Next: Wool or acrylic? →

Still have the ball band? Save the yarn to your stash with the Yarn Finder. No label at all? The whole method is in How to identify yarn without a label.