Knitting Cast-On Calculator
Enter head circumference, your blocked gauge per 10 cm, the negative ease, and your pattern's stitch multiple. The calculator gives the cast-on count adjusted to the multiple, the raw figure, and the finished relaxed width.
Ball-band gauges and generic tables create hats that fit nobody. This calculator uses your gauge and the physics of negative ease - the 2-3 cm by which knitted hats are deliberately smaller than the head.
How to use
- Measure the head where the brim will sit, above the ears - not the forehead, and round up half a centimetre for comfort.
- Swatch in the brim stitch, block it, and count stitches per 10 cm; enter that figure, never the band's.
- Pick your ease (2.5 cm is standard for ribbed brims) and the pattern multiple; knit an inch of brim and try it on before committing.
Frequently asked questions
What is negative ease in knitting?
The finished piece is smaller than the body it covers: knitted fabric stretches up to a third of its width and relaxes back, so a hat 2-3 cm under head circumference grips instead of sliding. Ribbed brims can take up to 5 cm; stiff stitch patterns barely 1.
Why did the multiple change my stitch count?
Ribbing, cables and lace repeat in fixed block sizes, so the cast-on must be a multiple of that block. The calculator rounds to the nearest multiple - if that shifts you more than 2-3 stitches from raw, change needle size rather than stretching the count.
Do I measure gauge before or after blocking?
After, always. Blocking usually widens and shortens stockinette, and the hat gets blocked too - the pre-block gauge is a number for a fabric that will never exist. For stretchy brims, measure the swatch slightly stretched as it will be worn.
How do I adapt this to a cowl or sweater band?
Same arithmetic, new circumference: measure where the piece sits, subtract the ease, multiply by stitches-per-cm. For pull-on cowls keep at least 2 cm negative ease or they slide; for sweaters follow the pattern's stated ease since it shapes the silhouette.