My new project is Elizabeth Zimmermann's Bavarian Jacket, one of her many clever garter stitch designs. It's an EPS (Elizabeth's Percentage System) pattern, which means that you take your gauge and multiply it by your wanted circumference to get your key number, K, and then everything that follows is a percentage of K.
So I found my K, cast on 50%, and knit the back. Then I knit the left front. Then the right front. Joined it all together. Knit up the collar. Ran i-cord around the whole mess, knit up the sleeves and started shaping the cap and that's when I realized...
... I've been shaping the armhole using percentages of the number of stitches I cast on for the back, 1/2K.
The only way to fix it would be to rip all of that i-cord, undo the seaming at the shoulders, and rip all three pieces back to armpit level.
I'm not going to do that.
Instead, I'll compensate. I had already compensated without realizing. When knitting the back, I noticed that my misreading of the directions gave me a very short armhole, so I pulled it back and lenghened it, and then I knit the fronts to match. Once I figured out my mistake, I also ripped back the sleeve so that I have three garter ridges instead of five before the sleeve cap shaping begins. And I've made sure that I used the right number to calculate how many sleeve stitches I should have.
Please excuse me while I go beat myself over the head with something heavy.