We use shoe size rather than calf circumference for sizing our compression socks because we have found that it is a better measure of fit for the majority of our customers.  It is possible that if your calf circumference varies greatly from the average person that these socks will not fit you.  If you are concerned that your calf might be too small/large for the socks, you might find that the Compression Leg Sleeves are a better choice for you.