This is the carpenters Golden Rule. It's also the knitters golden rule, or at least it should be. They call them Golden Rules for a reason. Know what happens when you don't follow them?
Note to self: When using leftover sock yarn to make baby socks, weigh the ball FIRST, divide it in half, then knit TOE UP. Sometimes - my DUH factor knows no bounds.
Now, the weight was fluctuating between 12.0 and 12.1 for the sock, and 11.9 and 12.0 for the yarn, so if I eliminate a couple of rows on the leg - I might just make it. Sigh.