Click to Open Rate (CTOR) is the percentage of people who open an email campaign and also click on a link within that campaign. CTOR compares the number of unique clicks to the number unique opens of an email. The CTOR calculates the effectiveness of an email campaign.

The click-to-open rate (CTOR) compares the number of unique clicks to unique opens. This number indicates how effective the email message, design, and content performed, and whether it created enough interest in the recipient to take action.

The best way to think about CTOR is to imagine, of those who opened your email, what percent found the content inside valuable/relevant enough to click on? It can be calculated as (unique clicks/unique opens) x 100. For example, if your email receives 100 clicks, and 150 opens, your CTOR is 66%