The Click-Through Rate (CTR) is a key performance metric in email marketing that measures how effectively your email content drives recipients to take action — typically by clicking a link, button, or call-to-action (CTA).
The formula for calculating email Click-Through Rate (CTR) is:

Note: Number of clicked links means Total number of clicked links including multiple clicks by the same recipient.
For example, 200 emails were successfully delivered, and 25 were link clicks, then the Click-Through Rate calculation will be:

Here, the Click-Through Rate is 12.5% which shows how engaging your content is. A higher CTR means more recipients are interacting with your email.