The widest part of my claves is 17.5' and these boots 'just' fit, but they were too snug. I was really dissapointed because I had seen people with larger calves than mine saying that these were great and fit them well. That was not the case for me which was quite dissapointing and confusing. So although they fit, they bunched up a lot in the ankle and just above the ankle which was unflattering. The boots themselves are gorgeous though but I unfortunatley had to return them and the hunt continues.
(For context, I ordered a size 8)