CO — Cast on (Abbreviation)
CO stands for "cast on" — the instruction that starts nearly every knitting pattern, telling you to establish your first row of live stitches on the needle before any actual knitting begins. "CO 80 sts" means create 80 stitches as your starting point.
Why CO alone doesn't tell you which method to use
Unlike more specific instructions, plain "CO" by itself doesn't specify a cast-on technique — long-tail, cable, and half a dozen other methods all satisfy a bare "CO 80 sts" instruction equally, since they all produce 80 live starting stitches. Some patterns are more specific ("using long-tail method, CO 80 sts"); many simply leave the method to the knitter's judgment or habit.
Choosing a method when the pattern doesn't specify
Long-tail is the reasonable default for most projects with no other constraint, since it's fast and reasonably stretchy. If the edge needs to stretch significantly (a ribbed brim or cuff), consider tubular cast-on or German twisted instead. If stitches will later need to be picked back up from this edge (a toe-up sock, a center-out design), a provisional cast-on is usually the right call regardless of what the pattern's plain "CO" implies.
Where it shows up
At the very start of a pattern ("CO 120 sts, join in the round"), and again mid-pattern anywhere new stitches need to be added rather than only at the beginning — a buttonhole, a sleeve gusset, a thumb opening.
Related abbreviations
- BO — bind off, the pattern's usual closing counterpart to CO
- st(s) — stitches, almost always paired directly with a CO count
FAQ
Does CO ever appear in crochet patterns? Rarely — crochet's equivalent starting instruction is almost always described as a foundation chain rather than abbreviated "CO," since the starting mechanics (chaining, not casting on) are genuinely different between the two crafts.
If a pattern's gauge doesn't match mine, should I change the CO count? Yes, generally — feed your own measured gauge into the Cast-On Calculator instead of using the pattern's stated CO count unchanged, since a different gauge needs a different stitch count to land on the same finished circumference or width.