How to substitute yarn in any pattern

The exact yarn in a pattern might be discontinued, out of your budget, only sold overseas, or simply not a fibre you can wear. Yarn substitution lets you use a yarn you already own — or one that fits your climate, allergies, or wallet — while still getting a garment that fits.

Done well, yarn substitution is mostly two questions: does the new yarn knit or crochet to the same gauge? and do you have enough of it? Everything below is how to answer both with confidence.

Find the gauge (also called tension) at the top of the pattern. It's usually written like this:

22 sts & 30 rows = 10 cm (4 in) in stocking stitch, 4 mm needles

Note three things: stitches per 10 cm, rows per 10 cm, and the needle or hook size. Stitch gauge is the number that matters most for fit — row gauge you can usually adjust by working more or fewer rows.

Start by matching the Craft Yarn Council weight category — the numbered symbol on the ball band from 0 (lace) to 7 (jumbo). Our yarn weight & gauge guide lists the typical gauge for each category.

Then check three details on the substitute's ball band:

• Recommended gauge — should be within 1–2 sts / 10 cm of the pattern.
• Meters (or yards) per 100 g — you'll use this to calculate yardage.
• Fibre — animal fibres bloom and bounce, plant fibres drape and grow, synthetics stay put. Match the family for garments where fit matters.

If you want the maths done for you, the Yarn Library filters by tension gauge and fibre and ranks candidates by how close they are to your target.

Ball-band gauge is a suggestion, not a promise. Cast on at least 10 cm more than the pattern gauge using the recommended needle size, work about 15 cm, then wash and block the swatch the same way you'll wash the finished piece.

Measure across the middle 10 cm — never right at the edges. If you have more stitches per 10 cm than the pattern, go up a needle size. If fewer, go down.

The formula is:

substitute yardage = pattern yardage × (pattern m per 100 g ÷ substitute m per 100 g)

Then divide by the meters per skein of your substitute and round up to the next whole skein. Add one more skein for safety — dye lots vary and a slightly denser fabric eats more yarn than the band suggests.

Rule of thumb: if the substitute is lighter per 100 g than the original (more meters), you'll need fewer grams. If it's heavier, you'll need more.

Sometimes you want to knit a DK pattern in worsted, or fingering held double in place of DK. It's doable — but the tighter you match gauge, the fewer surprises.

• Fingering ↔ sport: usually safe with a needle-size tweak.
• Sport ↔ DK: swatch carefully; a needle size up or down often lands within gauge.
• DK ↔ worsted: doable for accessories, risky for fitted garments — the fabric weight and drape change.
• Two strands held together: two fingering strands ≈ DK; two DK strands ≈ chunky. Always swatch.

Example 1 — Swapping wool for cotton in a summer tee

Pattern calls for 900 m of a DK wool at 210 m per 100 g. Your cotton DK is 180 m per 100 g.

900 × (210 ÷ 180) = 1,050 m needed

Your cotton is sold in 50 g balls (90 m each): 1,050 ÷ 90 = 11.7 → buy 13 balls (12 rounded up + 1 spare).

Example 2 — Same weight, different length

Pattern calls for 5 skeins of a worsted at 200 m per skein — 1,000 m total. Your substitute is a worsted at 160 m per skein.

1,000 ÷ 160 = 6.25 → buy 7 skeins