Yarn Weight Conversion Chart: US, UK, AU Ply, WPI, and Metric Counts Explained

A sourcing manager in Guangzhou reads a sweater pattern written for double-knit yarn, while a mill in Jiangsu quotes the same requirement as Nm 28/2. Across town, a hand knitter swaps an 8-ply for a 4-ply and watches the finished sleeve grow 6 cm beyond the schematic. Both problems trace back to the same gap: yarn thickness is labeled in at least four systems — CYCA numbers, US names, UK and Australian ply, and metric counts — and a yarn weight conversion chart is the only bridge that connects them.

This guide maps all four systems into one reference, with WPI ranges, gauge values, and mill-side counts. It is written for two audiences at once: designers and hand knitters who need to substitute yarn across borders, and production buyers who need to discuss thickness in the same language as a worsted-spinning mill.

What Yarn Weight Actually Measures

Yarn weight describes the thickness of a single strand, and thickness controls gauge, drape, density, and the total meterage you buy. It has nothing to do with the weight of the ball in your hand: a 50 g ball of lace-weight alpaca and a 50 g ball of jumbo cotton are both 50 g, yet they knit into completely different fabrics.

The numbered scale carries three practical facts at once: expected stitches per 10 cm, suggested needle or hook size, and typical wraps per inch. For an industrial buyer, the CYCA number also maps loosely to metric count, which is the language mills actually quote in.

Yarn Weight Conversion Chart: US, UK, Australian, and Metric Terms

Use this chart as the primary reference any time a pattern, spec sheet, or quote uses a weight name you do not recognize. Each row lists the CYCA category, the common US term, the UK or Australian ply, wraps per inch, a typical metric count, the stockinette gauge, and the suggested needle size.

Two columns deserve extra attention before you order production yarn. The ply column is not universal: UK 10-ply and Australian 10-ply are close but not identical across every mill, and the US rarely uses ply language at all — always confirm the target gauge rather than the ply number. The metric count column matters most to cost: Nm 7/2 to Nm 9/2 (roughly 350-450 m per 100 g) covers most fingering-weight sock yarns, while Nm 3/2 to Nm 4/2 is the usual band for worsted-weight knitwear. Typical metric counts vary by mill, so confirm meters per kilogram on the technical data sheet.

Wraps per Inch and Metric Counts: Two Languages for the Same Yarn

Wraps per inch (WPI) is the fastest physical measurement of yarn thickness, and metric count (Nm) is the fastest commercial one. WPI works without a label: wrap the yarn tightly around a ruler for two inches, count the strands, and divide by two. Metric count works without a sample: it states exactly how many meters one kilogram yields, which is the basis of yarn pricing at most mills.

Industrial orders, especially for worsted and blended yarns, quote metric counts (Nm) rather than consumer names. A US worsted-weight pattern usually sits between Nm 3/2 and Nm 4/2 in mill language, while a sock-weight yarn lands near Nm 7/2 to Nm 9/2. Understanding this connection lets you talk directly with a manufacturer about count, twist, and spinning method instead of translating vague terms like "DK" or "chunky" into production specs.

Using the Conversion Chart on Unlabeled Yarn

If the label is gone, three measurements settle the weight within ten minutes: wraps per inch, a 10 cm gauge swatch, and meters per 100 grams. Done in this order, they also cross-check each other, so a misread in one method gets caught by the other two.

1. Wrap the yarn around a ruler over a 2-inch span with the strands touching but not overlapping. Count the wraps, divide by two, and compare the result with the WPI column of the chart.
2. Knit a swatch at least 10 cm square with the needle size you plan to use, then count stitches across the middle. The gauge value reflects your personal tension and is a stronger signal than WPI alone.
3. Weigh the yarn and measure its total length. Meterage near 400 m per 100 g points to fingering weight, near 220 m to DK, and near 170 m to worsted.

These three checks are designed to confirm each other. WPI can mislead when a yarn is spun very soft or very dense, gauge catches that error, and meterage reveals the difference between a dense cotton and a fluffy wool that happen to share the same physical width.

Why the Correct Weight Conversion Changes Your Production Cost

In production, a one-category weight error can change the cost of the yarn in a garment by 20 to 35 percent, and it simultaneously alters shrinkage, drape, and surface durability. Because yarn is priced per kilogram, the metric count decides how many garments a kilogram covers: moving a spec from DK to worsted reduces the meters per kilogram and raises the yarn cost of every piece.

Professional buyers therefore convert consumer pattern language back into meterage before asking for a quote. When a designer requests a "worsted-weight" sweater yarn, the mill needs a target Nm, a twist level, and a fiber blend to price accurately. Mills with tight count control make this conversion stable from batch to batch; Jiangsu Haoye Fiber Technology Co., Ltd., for example, runs 20,000 spindles of Siro and compact worsted spinning and keeps production counts within tight tolerances.

Full Wool Easy Care Yarns from Jiangsu Haoye Fiber TechnologyThis supplier offers machine-washable all-wool yarns with softness and durability. With 20,000 spindles and tight count control, it suits buyers needing stable meterage conversion for worsted-weight projects.View Product →

Blending changes what the number means in the finished fabric. A wool-nylon sock yarn at the same metric count as a pure wool yarn wears longer and holds its shape better under abrasion, which is why durable socks are rarely spun from 100 percent wool alone.

Wool Nylon Yarn for Durable Knitwear and SocksBlending wool with nylon improves abrasion resistance and shape retention, making this yarn ideal for socks and high-wear garments. Clean stitch definition and predictable blocking suit pullovers and accessories.View Product →

For projects where clean stitch definition and predictable blocking matter — pullovers, cardigans, and accessories — a 100 percent wool yarn in the correct count range behaves more predictably than high-synthetic blends under steam and washing.

Pure Wool Yarn for Predictable Knitting and BlockingMade from 99.99% wool, this yarn offers warmth, breathability, and elegant texture. For projects requiring reliable steam and washing behavior, pure wool in the correct count range performs consistently.View Product →

If a pattern count and a mill quote still do not obviously line up, contact the mill and ask the technical team to confirm the conversion — a short conversation at sample stage is far cheaper than a rejected production lot.

Safe Yarn Substitution Rules When the Exact Weight Is Unavailable

Match the gauge target, not the category name, and buy 10 to 15 percent more yarn than the pattern calls for. Category names travel badly between countries; a measured gauge travels perfectly.

• Aim for a gauge within 1-2 stitches of the pattern target per 10 cm. Larger gaps change the finished size by whole garment sizes.
• Fiber content is the second variable: cotton does not spring back under blocking, wool does, and acrylic performs differently from both. The same gauge from different fibers produces different drape and warmth.
• If the substitute is heavier, you will need fewer stitches but more grams per garment. If it is lighter, recalculate stitch counts proportionally from the old gauge divided by the new gauge.
• Different dye lots are still a color risk even inside the same product line; buy all the yarn at once and verify the lot numbers match.

Yarn Weight Conversion FAQs