CTOR calculator (click-to-open rate)
Work out your click-to-open rate from unique opens and clicks. Formula, worked examples, and why Apple MPP inflates opens and drags CTOR down.
CTOR = unique clicks ÷ unique opens × 100
CTOR (click-to-open rate) is unique clicks divided by unique opens, times 100. It tells you what share of the people who opened an email found something worth clicking, which makes it the clearest single measure of whether your content did its job.
Use the calculator above with numbers straight from your email platform’s campaign report. If you only have rates rather than counts, switch it to percentages.
What click-to-open rate measures
Open rate tells you whether the subject line and sender name earned attention. Click rate tells you how many of everyone you sent to took action. CTOR sits between the two: it ignores everyone who never opened and asks only how the email performed with the people who actually saw it.
That makes it the metric to watch when you change the content of an email: the layout, the copy, the order of stories, the call to action. A low CTOR is a clear signal that the inside of the email isn’t giving readers a reason to click, however good the subject line was.
It’s also a useful check on a funnel. If an email exists to move people to the next step, such as a sign-up, a purchase or a longer read, CTOR shows whether it’s doing that for the people who engaged with it.
The CTOR formula
CTOR (%) = (unique clicks ÷ unique opens) × 100Use unique counts, not totals. One reader clicking five links counts once. For comparison, click rate (CTR) uses everyone you sent to as the base:
CTR (%) = (unique clicks ÷ emails delivered) × 100A worked example
You send a newsletter to 10,000 subscribers. 1,000 open it and 200 click a link.
- CTR is 200 ÷ 10,000 = 2%.
- CTOR is 200 ÷ 1,000 = 20%.
The same raw data can tell very different stories depending on which rate you read:
| Scenario | Sent | Unique opens | Unique clicks | CTR | CTOR |
|---|---|---|---|---|---|
| Moderate engagement | 10,000 | 1,000 | 200 | 2% | 20% |
| High opens, low clicks | 5,000 | 2,500 | 50 | 1% | 2% |
| Low opens, high engagement | 8,000 | 400 | 200 | 2.5% | 50% |
In the second row, the subject line worked and the content didn’t. In the third, the content worked for the few who saw it, so the problem is getting more people to open.
CTOR vs CTR
CTR is the broad view. It measures clicks against everyone who received the email, so it reflects the whole chain: deliverability, subject line, timing and content together. It’s the better number for judging a campaign overall.
CTOR isolates the content. Because it only counts people who opened, a change in subject line or send time barely moves it, while a change in what’s inside the email does. When you’re testing the email itself, read CTOR. When you’re judging the campaign as a whole, read CTR.
What a good CTOR looks like
Across industries, MailerLite’s benchmark data puts the average CTOR at 7.38%, ranging from 2.3% in software to 14.01% in construction. Publishing sits slightly above average at 8.88%.
Treat those figures as a rough guide rather than a target. CTOR varies a lot by format: a digest with a dozen links will usually beat a single-story essay, and a promotional send will behave differently again. The most useful benchmark is your own trailing average for the same type of email. A sustained drop against that baseline is worth investigating; a single low send usually isn’t.
Why Apple Mail Privacy Protection skews CTOR
Since iOS 15, Apple Mail can load email content, including the tracking pixel that records an open, through Apple’s servers whether or not the subscriber ever reads the email. Each of those machine opens counts as a unique open.
Because unique opens are the bottom half of the CTOR formula, those extra opens push CTOR down even when real engagement hasn’t changed. On a list where a large share of readers use Apple Mail, CTOR can look noticeably worse than it did before 2021 for no reason to do with the content. How Apple Mail Privacy Protection works covers the mechanics.
Clicks can be distorted too. Some corporate security filters follow links in incoming email to check them, which can register clicks nobody made and push CTOR up.
In practice:
- Check whether your email platform separates or filters machine opens and bot clicks, and use the filtered figures if it does.
- Compare CTOR over time on the same basis. Don’t compare a pre-2021 send with a current one.
- For lists heavy in Apple Mail, give more weight to clicks and CTR, which privacy features don’t inflate.
How to raise CTOR
- Put the main link early. A call to action that sits below several screens of text gets a fraction of the clicks it would get near the top.
- Make one action obvious. If everything is a link, nothing stands out. Decide what you most want readers to click and make it the clearest thing in the email.
- Deliver what the subject line promised. People open for the subject line. If the email doesn’t follow through on it, they don’t click.
- Segment by interest. Content matched to what a reader has engaged with before gets clicked more than a single edition sent to everyone.
- Design for mobile first. Most opens happen on a phone. Tap targets that are too small or too close together cost clicks.
- Test one change at a time. Layout, link placement and call-to-action wording all move CTOR. A/B test them separately so you know which change worked.
- Cut what nobody clicks. Your platform’s click map shows which sections earn clicks. Sections that never do are taking space from ones that might.