Unique Clickers / Opens = CTOR %
The click-to-open rate, or CTOR, is calculated by dividing the total number of unique clickers by the total number of opens. Why not divide by clicks? Clicks is a higher number because it not only includes unique clicks, but repeat clicks as well.
MESSAGE ACTIVITY REPORT
In the message activity report, Total Clicks represents the number of unique clickers. The unique clickers are broken down into Repeat, contacts who have clicked a link in a previous send, and New, contacts who clicked a link for the first time in this send.
In the conversation analytics report, we see a slightly different breakdown, however, we can still find the number of unique clickers. Here it is represented in the Clickers.