Are you sure that you are measuring in the very same spot as before and did you hold the tape tighter the first time? Did you measure the same calf-ie left or right?
I lost almost 40lbs and my calves only went down an inch. However, I lost 7.5 on my waist in comparison. What I do is measure everything. It is amazing where you lose inches on. This is what I do:
neck, above bust, bust, waist, belly, hip, upper thigh, knee, calf, ankle, upper arm, elbow, and wrist. I lost 37 inches all over. They all count. Try it and DO NOT get discouraged!!!