what's a formula?

my knitting room floor is littered with waste yarn debris and defective bands - I just finished my KnS project for the September (or is it October?) issue - I had to make the front bands FIVE times to get two good ones!!! what on earth is that all about??? well, mostly, not paying attention and not using the mid gauge enough - different rules apply - on the standard gauge, pretty consistently, when making a stockinette band, like for the fronts of a cardigan, you simply hold the length of your piece up to the needle bed evenly, without stretching, and that’s the number of stitches needed to make the band (based on a 4 ply weight yarn that is knitting about T7). But, on the mid gauge, this little trick doesn’t work quite as well. Now, I could, of course, do some research and look up what I’ve done before - makes sense, but no, that would be too easy, almost like cheating! So, the first band (estimated as above - 97 sts - an uneven number because it’s easier to cast-on an uneven number on the LK), after attaching, pulls up a bit - no big deal, I can handle that. Add a few stitches and build a new one; get it attached to the other side and look at it - the length is perfect but I forgot to figure on the angle at the neckline - why didn’t I notice that on the first one? Now, to get serious and actually do a bit of figuring and come up with a method that could be used by others: calculate the length of the band - take the number of rows from hem to neck of actual knitting and divide by the row gauge and it gives me 20.75 inches (yeah, for KnS, I’m working inches), multiply that by my stitch gauge and get 114 sts - I know that will be way too long compared to my first attempt, so use a 10% reduction factor, which results in 102 sts - add one for the uneven thing and I have exactly what my second band was. Okay, we’re good! Make the band without thinking it through, decrease at one end for the angle - crud!! that’s the wrong way - need to start with more and decrease to the 103 sts...
I haven’t actually described this band, but it begins with the chain cast-on (after waste yarn, of course), knit 8 rows; RTR (remove, turn, rehang), K1R - for a garter stitch row which makes a join to the edge - this is really a facing that is on the outside of the cardigan front. Then this piece is taken off (TGIHAGB- thank god I have a garter bar); the garment front is hung, right side facing; the band is rehung, pulling the open sts through the closed edge. THEN, RTR (so the chain shows on the outside) again, knit a loose row and chain off...
You know it  - I had a day off in between and screwed up on the angled ends, made the same one twice...then, even though I’m positive I religiously used the row counter, the fourth band, after attaching, looked a little wide - sure enough, it was 10 rows, but I liked it! Very carefully made the opposite one the same but opposite if you know what I mean - it looks beautiful!
I want to see them turn this into a hand knitting pattern! BTW, the yarn here is Plymouth Yarns DK Merino Superwash - LOVE IT!!! this will be my new go-to DK wool for the LK, for sure - it has a lovely twist to it that gives excellent stitch definition and is a pleasure to work with!