If I did the math right (knitting math, hmmm) I have the calf increasing to fit my larger calf. I have been increasing at the back almost every round. This should, un-stretched, be about 19" (yes, I have huge calves). This should fit with a little stretching.
This is why I'm trying to learn how to knit socks. I have very large calves so forget about finding any knee socks that actually fit in the store.