CTOR
Click-to-Open Rate
Quick definition
Click-to-open rate (CTOR) is the percentage of recipients who opened an email who also clicked a link, calculated as unique clicks divided by unique opens.
Formula
CTOR = Unique Clicks ÷ Unique Opens × 100
Formula variables
- Unique Clicks
- Recipients who clicked at least one link.
- Unique Opens
- Recipients with at least one recorded open.
Worked example
- Unique opens
- 2,500
- Unique clicks
- 300
300 ÷ 2,500 × 100
Result: 12%
Of the people recorded as opening, 12% clicked. The figures are illustrative, not a benchmark.
How to interpret it
CTOR isolates how persuasive the content was among people who saw it, separate from the subject line and sender that drove the open. That makes it useful for comparing email content.
It inherits the weaknesses of open rate: if opens are inflated, CTOR is understated.
When it is useful
- Comparing email layouts and calls to action.
- Separating content performance from subject-line performance.
- Diagnosing whether low clicks come from low opens or weak content.
Limitations
- Depends on open tracking, which is not fully reliable.
- Differs from email CTR, which uses all delivered emails.
- Small numbers of opens give unstable rates.
Common mistakes
- Comparing CTOR with email CTR.
- Ignoring changes in open tracking behaviour.
- Using CTOR alone to judge a campaign.