I’m ready to finish my project :woohoo: I will be using the Kitchener stitch, the needles I am working off of are number 11’s and the yarn is a worsted, held doubled, and there are 34 stitches.
TIA
ideally you will have left a tail on one of the pieces of knitting that’s at least twice as long as the finished join will be.
From the paragraph above the 1st picture in the article which is talking about stockinette. If there are purls involved, you might need to allow more.
My thinking is that as you’re pretty much inserting a row of knitting, however much it takes for those 34 sts plus a tail to weave in should be about right. I prefer to err on the side of too much allowed whenever possible.
If I had only read this before I began this project:
With the provisional cast-on you have one less stitch at the beginning of your project than at the end and you need an equal number of stitches for the Kitchener Stitch. I plan to tink back on the last row and p2tog in the middle of the row. 
this works 
Kelley Petkin from KnitPicks leaves 3 times the length on her Kitchener sock toes, but then again she works the Kitchener loosely, and snugs the stitches up later. YMMV…
I found a solution to the one less stitch thing. I use the same cast on as I do for sock toes, Judy’s Magic Cast-On and hold the unused stitches on a cable or waste yarn. There may be good reasons for not doing this but so far I’ve had no problems and I have the same number of stitches to work with.
grafting uneven numbers of stitches together
It’s mostly about sock toes but it can be applied other places as stated toward the end of the article.
Ehh. I just pick up an extra stitch or fudge it and I’ve never had a problem. Of course with heavy yarn that might not work.