That Yarn · Journal

How to Substitute Yarn in Any Pattern: A Systematic Method

Gauge is the first test, not the only one. A five-step method for matching yarn to pattern — and for knowing when a substitution will quietly fail.

Every maker eventually faces the same moment. The pattern names a yarn that is discontinued, unavailable, or simply not what you want to work with. The instinct is to find something with the same weight on the label and begin. Sometimes that works. Often the finished garment drapes wrong, grows in the wash, or feels nothing like the photograph.

The problem is that weight categories describe only one property of yarn — roughly how thick it is. A pattern relies on several others: how the yarn behaves under tension, how much it weighs for its bulk, how it recovers, how it changes when wet. Substitution done well accounts for all of them.

What follows is a method. It moves from the property that is easiest to verify to the one most often ignored. Work through it in order, and you will know before casting on whether a substitution is sound.

Step one: match gauge, not weight category

Weight categories are a retail convenience. "DK" covers a wide band of yarns, and two yarns sitting in the same band can knit to noticeably different gauges. The pattern does not care what the label says. It cares about stitches per inch.

So begin with the pattern's stated gauge, not the pattern's stated yarn. If a pattern calls for 22 stitches over 4 inches on 4mm needles, your task is to find a yarn that produces 22 stitches over 4 inches on a needle near 4mm — at a fabric density you are happy to wear.

That last clause matters. A finer yarn can be forced to gauge on larger needles, but it will produce a loose, airy fabric. A heavier yarn can be forced to gauge on smaller needles, but it will produce a dense, board-like one. Gauge is necessary. It is not sufficient.

Gauge match = stitch count + fabric density you actually want

Working from Nm

For cone yarn, the label gives you Nm rather than a weight category, which is more precise. Convert to meters per 100g, then read across to the category the pattern implies. A yarn at 400 meters per 100g sits in fingering territory; one at 220 sits in DK.

If you are unfamiliar with reading Nm counts, our guide to yarn weight and Nm covers the conversion in full, including how to ply single strands to reach a heavier weight.

Treat gauge ranges as orientation, not law. Fiber and construction move a yarn within its band, and sometimes across the boundary.

Step two: match yardage, not grams

Patterns state quantity in two ways: total length, and number of skeins. Only the first is reliable.

A skein is a packaging decision. Two yarns of identical weight category can carry very different lengths in the same 100g put-up, because fiber density differs. Alpaca is heavier per unit of bulk than wool. Mohair is far lighter. Cotton is heavier than both. Substituting skein-for-skein can leave you short by hundreds of meters.

Total meters needed = pattern's stated meters × 1.10

The ten percent margin covers swatching, gauge drift, and the fact that most makers knit slightly looser at the end of a project than the beginning. For colourwork, cables, or anything with substantial texture, raise it to twenty percent. Those structures consume more yarn per stitch than stocking stitch, and patterns do not always account for the difference generously.

If the pattern gives only skein counts, find the original yarn's meters per skein, multiply, and work from that number. Never buy by skein count alone.

Step three: match fiber behaviour

This is where most substitutions quietly fail. Two yarns can share gauge and yardage and still produce entirely different garments, because fiber determines what the fabric does after it leaves the needles.

The property to reason about is memory — the fiber's ability to return to shape after being stretched. Wool has considerable memory, because its crimped structure acts as a spring. Alpaca, silk, and most plant fibers have very little. Fabric knit from low-memory fiber will grow under its own weight and stay grown.

The practical rule

A pattern written for wool, worked in alpaca or silk, will produce a longer, heavier, more fluid garment than intended. This is not always wrong — a fitted wool sweater reinterpreted in a drapey blend can be lovely — but it must be a decision, not a surprise.

Substituting in the other direction is safer. A pattern written for a drapey fiber, worked in wool, will hold its shape more firmly than the designer imagined. The garment will be closer to the schematic, if less fluid than the photograph.

Blends sit between. A wool-silk yarn behaves like wool with reduced memory; the higher the silk content, the more it will grow. Read the percentages, and weight your expectation toward the dominant fiber.

Step four: match construction

Fiber is what the yarn is made of. Construction is how it was made — and it shifts behaviour as much as fiber does.

Ply structure

A round, multi-plied yarn produces crisp stitch definition and even fabric. Cables, textured stitches, and colourwork all rely on this. A single-ply yarn is softer and haloed but obscures stitch pattern, and may bias — lean diagonally — because its twist is unbalanced.

If the pattern's photograph shows sharp cables and your substitute is a single, the cables will blur. If the pattern is a simple stocking-stitch shawl, the single may be the better choice.

Spinning system

Worsted-spun yarn is combed so the fibers lie parallel. It is smooth, dense, strong, and shows stitches clearly. Woollen-spun yarn is carded so the fibers lie every which way, trapping air. It is light, lofty, warm, and fuzzy.

Two yarns of identical fiber and identical gauge can differ substantially in weight and warmth for this reason alone. A worsted-spun DK will make a heavier, denser garment than a woollen-spun DK at the same stitch count.

Brushed and haloed yarns

Mohair, brushed alpaca, and similar yarns bloom after washing — the halo opens and the fabric closes. Gauge measured on an unwashed swatch will mislead you. Always wash and dry the swatch before measuring these yarns.

Step five: swatch, wash, and measure again

The swatch is not a formality. It is the only place where all four previous steps are tested at once, and the only honest source of information about how the finished fabric will behave.

1. Knit a swatch at least 6 inches (15 cm) square. Smaller swatches lie, because edge stitches distort the count.
2. Work it in the pattern stitch, not stocking stitch, unless the pattern's gauge is given in stocking stitch.
3. Measure and note the gauge before washing.
4. Wash the swatch exactly as you intend to wash the garment. Block it as you intend to block.
5. Dry it flat, undisturbed, until completely dry.
6. Measure again. Compare to the pattern.

The change between the two measurements is the most valuable number you will get. It tells you whether the yarn grows, shrinks, blooms, or holds. A wool swatch may tighten slightly. A cotton swatch may lengthen. A cashmere swatch may open by a full stitch as the fibers relax.

Hang the wet swatch from a clothespin for an hour before drying. If it stretches and stays stretched, the garment will do the same — under the weight of its own fabric, over years of wear.

A note on cone yarn

Industrial cone yarn often arrives with spinning oil or wax still on the fiber, applied so it runs smoothly through machinery. Unwashed, it feels thinner, harder, and less lofty than it truly is. A swatch measured before washing will tell you almost nothing.

Wash the swatch. The yarn will bloom, soften, and often gain a stitch or two per four inches. This is the yarn's actual character, and it is the one your garment will have.

When substitution is not worth it

Some patterns depend so completely on a specific yarn that substitution changes the design rather than the material. Recognising these saves disappointment.

• Structural colourwork at fine gauge relies on wool's grip and elasticity. Superwash, silk blends, and plant fibers will not hold floats evenly.
• Steeked garments require non-superwash wool that felts slightly at the cut edge. No substitute is safe here.
• Patterns designed around a halo — mohair-heavy shawls, brushed layering pieces — lose their entire visual logic in a smooth yarn.
• Deeply cabled sweaters in a low-memory fiber will stretch out of their cables and never return.

In each case the answer is not to force the substitution. It is to find a yarn from the same family, or to choose a different pattern.

The method, condensed

Five questions. The first four can be answered at the shelf or the screen. The fifth requires an afternoon and a small square of knitted fabric — and it is the one that decides whether the garment is worn or folded away.

Frequently asked questions