Yarn Weight Converter

Convert between the US yarn weight numbers, the UK and Australian ply names, and wraps per inch.

The same yarn can be called worsted, aran, medium or a number 4 depending on where the pattern was written. This converter lines up the US numbers, the common UK and Australian names, and the wraps per inch measurement you can take yourself, so you can substitute with confidence.

At a glance

What you enter: Yarn weight
What you get: US weight number, Suggested needle, Suggested hook, Reference gauge, Typical skein length
Formula shown: Yes, every step, right below your results.
Cost and privacy: Free, no account needed, and nothing you type is stored.

See worked examples ↓ Read the FAQ ↓ Share this calculator ↓

Yarn weight

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US weight number 1

Suggested needle 2.75 mm

Suggested hook 2.25 mm

Reference gauge 27

Typical skein length 400

How is this calculated?

Each yarn weight class is a published range. The wraps per inch figure here is the middle of that range.

The US number, the ply name, the suggested needle and hook and the reference gauge all describe the same class, so they are internally consistent with each other.

The ranges overlap and fibre blends behave differently, so classification by wraps per inch is a guide rather than a verdict. Weighing a known length is more precise.

Wraps per inch: 20

Your numbers stay in the address bar, the link reproduces this exact calculation.

Results are estimates for general information only, always verify with a professional or official source before acting on them.

How to use the Yarn Weight Converter

1 Enter Yarn weight
2 Press Calculate. You get US weight number, Suggested needle, Suggested hook, Reference gauge, Typical skein length, and every intermediate step stays visible under "How is this calculated?"
3 Change one number at a time to see what moves the result, that is usually the most useful thing a calculator can tell you.

Worked examples

Real numbers run through this calculator. Open any example to load it into the form above and change it.

Band says worsted

You have a US pattern written for worsted and want the UK name.

You enter

Yarn weight: 5

You get

US weight number: 4
Suggested needle: 5.00 mm
Suggested hook: 5.00 mm
Reference gauge: 18
Typical skein length: 200

Check the gauge on your band against the reference above.

Open this example in the calculator →

Sock weight for a shawl

You are substituting super fine yarn for a pattern written in lace weight.

You enter

Yarn weight: 2

You get

US weight number: 1
Suggested needle: 2.75 mm
Suggested hook: 2.25 mm
Reference gauge: 27
Typical skein length: 400

Two classes heavier, so expect the fabric to be denser and the yardage lower.

Open this example in the calculator →

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Frequently asked questions

What is worsted weight in UK terms?

Worsted is US weight 4. In the UK and Australia the nearest names are aran or 10 ply, though aran is sometimes slightly heavier. Treat worsted, aran and 10 ply as a family rather than exact synonyms, and match the gauge on the pattern rather than the name on the band.

How do I measure wraps per inch?

Wrap the yarn around a ruler, snugly but without stretching it, until you have covered exactly one inch. Count the strands. Do not squash them together and do not leave gaps. Five wraps per inch is bulky, twelve is DK, eighteen is closer to sock weight.

Is DK the same as 8 ply?

Very nearly, and in Australia the terms are used interchangeably. Both sit at US weight 3 with a reference gauge near 22 stitches per 4 inches. Small differences between brands mean you should still swatch.

What happens if I substitute a different yarn weight?

The fabric changes. Going up a weight makes a denser, stiffer fabric and going down makes it drapier and looser. If you substitute, work a swatch, match the gauge the pattern asks for, and expect the yardage to change. Use the yarn calculator to check whether the substitution still fits your project.

Terms used here

Short, plain-language definitions of the words this calculator uses.

Wraps per inch A way of classifying an unknown yarn by winding it around a ruler for exactly one inch, snugly but without stretching, and counting the strands. Yarn weight A category describing how thick a yarn is, published as a numbered system from 0 (lace) to 7 (jumbo) with an equivalent name such as fingering, DK, worsted or bulky.

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