How to convert a knitting pattern to your yarn and gauge
The pattern was written for one gauge and your yarn knits to another — that is how most ill-fitting sweaters start. Converting takes a minute once you know the formula and two rounding rules.
The formula
Gauge is how many stitches (and rows) fit in 10 cm (4 in). To move a number from the pattern to your yarn:
Your number = pattern number × your gauge ÷ pattern gauge
Example: a pattern at 18 sts per 10 cm says cast on 88. Your swatch gives 22 sts per 10 cm: 88 × 22 ÷ 18 = 107.6. Round to 108, a multiple of 4, so 2×2 rib meets in the round.
Check in centimetres: 88 sts at 18 per 10 cm is 48.9 cm and 108 sts at 22 per 10 cm is 49.1 cm — the same width.
Rows: convert them, or knit to length
Rows use the same formula with the row gauge, but it is easier to knit lengths in centimetres: “work 40 cm to the armhole” does not depend on the yarn. You must convert rows wherever they define the shape: sleeve increases (“every 8th row”), the sleeve cap, raglan lines and short rows.
For example, a sleeve going from 44 to 74 sts over 120 rows is 15 paired increases every 8 rows. With another yarn both the stitch and the row counts change, so work out the increase rate again rather than copying “every 8th row”.
Two rounding rules
- Round to the stitch pattern. 2×2 rib in the round — a multiple of 4, 1×1 — of 2, a 12-stitch cable — a multiple of the repeat plus edge stitches. The calculator has a “multiple” field for this.
- Do not round the gauge. 21.3 sts per 10 cm is not “about 21”. On a 100 cm sweater 0.3 st per 10 cm is 1.5 cm of chest, and 0.5 st is 2–3 cm.
When converting is not enough
If the yarns are very different (a pattern at 14 sts, your yarn at 26 sts), the fabric drapes differently and the yardage changes completely. Then it is faster to calculate the sweater for your own gauge and measurements — the builder does every section at once.
Always measure gauge on a washed swatch: how to knit and measure a swatch.
FAQ
How do I convert a pattern for thicker yarn?
The same way: pattern number × your gauge ÷ pattern gauge. Thicker yarn gives fewer stitches per 10 cm, so you get fewer stitches — 120 sts at 24 per 10 cm becomes 120 × 18 ÷ 24 = 90 sts at 18 per 10 cm.
Can I just change needle size?
Sometimes: if you are 1–2 sts per 10 cm off, a swatch on larger or smaller needles may match the pattern gauge. The fabric will get firmer or looser, so check a washed swatch.
What about the stitch-pattern repeat?
After converting, round to a multiple of the repeat (plus edge stitches). If rounding changes the width by more than 2 cm, change the number of repeats or the gauge instead.
How much yarn at a different gauge?
Different from the pattern: finer yarn uses more metres. See “How much yarn for a sweater” for estimates.