How to dec evenly

Hi, starting a toddler hat (off the top of my head) did a k2, p2 rib for about 2", then st for probably 9"…I have 115 sts (in the round) so at how do a start to dec for the crown evenly? And how do you mathematically figure that out? Taking the number of co sts, dividing them for an even amt of dec sts? I know how to dec and I checked other patterns and too me it looks like some sort of calculations…thx

It helps when your number is easily divisible by 2 other ones, and 115 isn’t. You could do a round that decreases 7sts evenly spaced to get you down to 108 sts. Then do the crown decs as k10, k2tog 9 times around, and one plain round. On the next one it would be k9, k2tog, 9 times around and a plain round after that. Keep that up, knitting 1 less stitch between the decs every other round until you’re down to about 4 sts between the k2togs, then dec every round. When you’re at about 18 sts, you could cut the tail and pull it through the last of the stitches, or if that’s too many, then k1 k2tog one more round so you have 12 stitches and finish it off.

eta - I got to thinking you might need fewer decrease rounds so it wouldn’t be too long, so you could do an initial decrease of 5 sts to 110 sts, then start with either k8, k2tog 11 times, or k9, k2tog 10 times. Then still do a plain round between the dec rounds and 1 less stitch between decs.

Thank you, so what is the equation, do you divide your sts in half and come up with a number to start decs? Or just start with the number 10 and work down no matter how many sts you co?

It’s not a set formula, though I’m sure algebra geeks could make one… For a hat, the decs work out best if you dec 7, 8, 9 or 10 sts every other round, it depends on your gauge and how long you need to end up with. So you would find a number that’s divisible by one of those, or adjust your sts so they are, then since the dec uses 2 sts you would knit 2 less than the other divisor. That’s why in my examples, 108 is a multiple of 9 x12, so for 9 decs, you’d k10, k2tog (12 sts) on the first round. For 110, you can either do k9, k2tog (11 sts) 10 times, or k8, k2tog (10 sts) 11 times. Then on the following decrease rows you k1 less stitch between the decreases.