Click-to-Open Rate (CTOR) is important in email marketing because it tells you whether your content actually engages readers and motivates them to take action. It helps you improve email design, messaging, and overall engagement quality. It mainly shows how effective your email content and call-to-action (CTA) are after the email is opened.
The formula for calculating email Click-to-Open Rate (CTOR) is:

For example, if the recipients opened 2,000 emails and 300 is the number of unique recipients who clicked at least one link, then the calculation for CTOR will be:

This shows your Click-to-Open Rate is 15%. This reflects how engaging and relevant your content is to the audience.