Formula
Gauge is measured over 4 inches, which is 10 centimetres. The cast-on for a width multiplies that width by your stitches and divides by 4. Knitting the pattern’s cast-on at your gauge divides the other way.
cast-on = target width × your stitches ÷ 4
finished width = pattern cast-on ÷ your stitches × 4
percent = (yours − pattern) ÷ pattern
A negative percent means your swatch has fewer stitches or rows than the pattern in the same 4 inches. The piece will be larger than the pattern’s schematic if you use the pattern’s numbers.
Worked examples
18 stitches per 4 in, pattern says 20, target width 20 in. Cast on 90. The stitch gauge is (18 − 20) / 20 = −10%.
Pattern casts on 100. At 18 stitches per 4 in that fabric is 100 / 18 × 4 = 22.22 in wide. At the pattern’s 20 stitches it would have been 20 in.
140 pattern rows at 24 rows per 4 in. Length is 140 / 24 × 4 = 23.33 in. The pattern’s 28 rows per 4 in would have been 20 in.
Reference
Target width 20 inches. Pattern gauge 20 stitches and 28 rows per 4 inches. Cast-on if you match the width; percent if you do not match the gauge.
| Your sts / 4 in | Cast on | vs pattern |
|---|---|---|
| 16 | 80 | -20% |
| 18 | 90 | -10% |
| 20 | 100 | 0% |
| 22 | 110 | 10% |
| 24 | 120 | 20% |
Questions
How many stitches do I cast on for a width?
Target width times your stitches per 4 inches, divided by 4. At 18 stitches per 4 inches, a 20 inch piece is 90 stitches. The same formula works in centimetres if you measure the gauge over 10 centimetres, which is the 4 inch swatch.
What if I knit the pattern’s cast-on at my gauge?
Finished width is the pattern cast-on divided by your stitches per 4 inches, times 4. A pattern that casts on 100 at 18 stitches per 4 inches finishes at 22.2 inches, not the 20 inches that 20 stitches per 4 inches would have made.
How is the percent difference signed?
It is (your gauge − the pattern gauge) ÷ the pattern gauge. Eighteen stitches against a pattern’s 20 is −10%: your fabric has fewer stitches in the same 4 inches, so it is looser and wider.
Sources
- Stitches for a width = target width × (stitches per 4 in) ÷ 4. Four inches is the 10 cm swatch.
- Width at your gauge = pattern cast-on ÷ your stitches × 4. Percent difference = (yours − pattern) ÷ pattern.