What is WPI (wraps per inch)?

WPI stands for wraps per inch. To measure it, wrap your yarn around a ruler without stretching or overlapping, and count how many wraps fit in one inch. A higher WPI means a finer, thinner yarn; a lower WPI means a thicker yarn.

How do ply numbers relate to yarn weight?

Ply refers to the number of twisted strands in a yarn. Historically, 4-ply meant fingering weight and 8-ply meant DK weight. However, modern ply numbers are not always consistent across brands — WPI is a more reliable measurement of actual thickness.

Can I substitute a yarn in a different weight category?

Yes, but you will need to adjust needle or hook size and your gauge swatch will differ. Always knit or crochet a gauge swatch and block it before starting your project to confirm your stitch and row counts match the pattern.

Why do US and UK yarn weight names differ?

The US and UK developed separate naming conventions historically. For example, what the US calls "sport" weight, the UK often calls "4-ply," and US "worsted" roughly maps to UK "aran." This converter uses the Craft Yarn Council (CYC) standard categories (0–7) which are widely adopted internationally.

What yarn weight should beginners start with?

DK (weight 3) or worsted (weight 4) are recommended for beginners. They are thick enough to see stitches clearly and work up quickly, but fine enough to keep projects manageable. Bulky or super bulky yarns are also beginner-friendly because they work fast on large needles or hooks.

Yarn Weight Converter

Select a yarn weight category to instantly see WPI range, ply equivalents, and recommended knitting needle and crochet hook sizes.

Select Yarn Weight

Choose a category or enter your WPI count to identify your yarn.

Weight Category

Or enter your WPI (wraps per inch)

Select a weight category or enter a WPI count to see the full specification.

Full Yarn Weight Reference Table

Click any row to load its details on the left.

#	Name	WPI	Ply	Needle (US)	Needle (mm)	Hook (US)	Hook (mm)

Summary

Yarn weight is a standardized system for classifying yarn thickness. Different countries and manufacturers use different labels — lace, fingering, sport, DK, worsted, bulky, and super bulky — and each maps to a specific range of wraps per inch (WPI) and ply counts. This converter lets you select any weight category and immediately see its full specification, including the recommended US and metric knitting needle sizes and crochet hook sizes.

How it works

Select a yarn weight category from the dropdown or click one in the reference table.
The tool instantly shows the WPI (wraps per inch) range for that weight.
Ply equivalents (2-ply, 4-ply, 8-ply, etc.) are displayed alongside.
Recommended US and metric knitting needle sizes appear in the results.
Recommended crochet hook sizes (US letter and metric mm) are also shown.
Use the full reference table below to compare all weights side by side.

Use cases

Identify the weight of an unlabeled yarn by counting wraps per inch.
Find substitute yarns in a different weight category for a pattern.
Determine the correct needle or hook size when starting a new project.
Convert between US, UK, and Australian yarn weight naming conventions.
Quickly reference ply equivalents when shopping for yarn internationally.
Check compatible hook sizes before swatching a new crochet project.
Teach beginners how yarn weight categories map to needle and hook sizes.
Confirm that a yarn label matches the weight called for in a pattern.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu