What Is Click to Open Rate (CTOR) In Email Marketing?

April 24, 2024
Written by
Jesse Sumrak
Opinions expressed by Twilio contributors are their own

What Is Click to Open Rate (CTOR) In Email Marketing?

Click-to-open rate (CTOR) is one of the single best email marketing metrics for gauging your email campaign's performance. And it's not as daunting as it looks. Below, we'll walk you through everything you need to know about CTOR, including what it is, the click-to-open rate formula, and differences with other metrics.

What is click-to-open-rate (definition)

The best way to think about CTOR is to imagine, of those who opened your email, what percent found the email content inside valuable/relevant enough to click on?

As marketers, we understand that the email we’re sending must be intriguing, relevant, and desirable. But we have to remember that email is supposed to be a win-win—brands send more emails, and consumers get to see more offers/info relevant to their wants, needs, and actions they’ve taken.

You don't just want people to open your emails. You want them to open and take action.

And that's what click-to-open rate tries to calculate. It's the ultimate measure of your email performance.

Click-to-open rate formula

This is how to calculate click-to-open rate in seconds. Your click-to-open rate 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%.

CTOR: (100/150) x 100 = 66%


Although metrics like open rates are equally important to track, CTOR helps paints a more complete picture of how your content is performing.

And on the other hand, you have click-through rate (CTR). CTR measures the click-through rate for everyone you sent the email to—whether they opened it or not. This metric can be a tad misleading because low email open rates will always correlate with low click-through rates, but that information doesn't give you the insights you need.

For example, you might have a low open rate because of a poor email subject line or bad sending timing—but that doesn't necessarily mean the content of your email or the calls to action (CTAs) were bad.

CTOR vs CTR: CTOR is based on people who opened your email rather, while CTR measures the number of unique clicks of your entire recipient list (your total number of subscribers)

Keeping a close eye on your CTOR ensures that you can determine if your content is actually resonating with your email recipients (once they were convinced to open your email).

What is the average click-to-open rate?

Generally speaking, a good CTOR can range between 20% and 30%. However, as with any metric, it’s important to know how you compare with your industry averages. Refer to our 2018 Global Email Benchmark Report to see how you compare to your industry average on unique click to open rate.

How to increase your click to open rate (CTOR)

In order to optimize your CTOR, start with these 5 steps:

1. Calculate your baseline CTOR

If you’re tracking your emails on a campaign level, find your norm for each of your different campaign types. Campaigns with personalized offers will have a consistently higher CTOR, so make sure you’re comparing apples to apples.

2. Incorporate more personalization

Giving customers something relevant and personalized to them will undoubtedly result in more clicks once your customers have opened your email. Use whatever data you have such as pages, products viewed, or products favorited, etc. to serve them something specific to their tastes.

3. Perfect your subject line

Every email marketer shoots for a subject line that will get them the highest possible open rate. I definitely get a feeling of excitement when I think of a clever, or funny subject line, but subject lines serve a bigger purpose than just a “wow” factor.

Opens are great, but only as great as how close it gets you to the final goal: conversion.

If your subject lines are getting opens because they’re funny or abstract but not because they are representing your copy appropriately—they could cause your email to bounce, so consider providing a more clear and direct subject line. 

Ultimately, it's all about your conversion rate. Other things can just be distractions along the way. 

 4. Provide a persuasive CTA

Focus on including clear and concise calls to action. Make sure your openers know exactly what you’re asking of them.

Read up on Your Top Email Call To Action (CTA) Questions, Answered to make sure you’re covering all your bases.

5. Review your results

When you are reviewing your email campaign metrics, the CTOR is great at gauging how relevant or valuable the content within your email appeared to the recipient. If you see high open rates, but low CTOR rates, this indicates that you nailed the subject line, but left more to be desired on the offering or copy within your email.

On the flip side, if you’re seeing lower than normal open rates, but increasing CTOR, then you can infer that you’re providing recipients with quality content and offerings. To balance these two elements, ensure that you’ve segmented your email list so that your campaigns are fine-tuned and targeted towards the right recipient groups.

6. A/B test variables

A/B testing (sometimes called split testing) lets you systematically compare two versions of your email. Whichever performs the best (has the highest click-to-open rate), you can send to the bulk of your email list.

Focus on isolating and testing one variable at a time. This might be your subject line, CTAs, or email layout. See which changes have the biggest impact on your CTOR, and record the findings to use in future email marketing campaigns, too.

7. Segment your email list

The best way to improve your click-to-open rate is to send relevant emails to your audience—and that starts with segmentation. Start by organizing your email list into groups based on shared characteristics:

  • Location
  • Purchase history
  • Last engagement
  • Subscription data

This approach turns a generic email blast into personalized conversations. Why send a snow gear promo to the sunny folks in Florida? Or why send an event signup reminder to those who've already registered?

Don't. Just don't.

Remember, when it comes to your email marketing strategy, one size does not fit all.

8. Watch your unsubscribes

Keep an eye on your unsubscription rate—it's like reading the room at a party. If you see unsubscribes climbing, double click to check whether the frequency, relevance, or timing of your email campaigns are off. 

Are you sending too many emails, or are they missing the mark on what your audience truly cares about?

Don't take it personal. Instead, use unsubscribes as data to refine your digital marketing strategy. Experiment with adjusting how often you send emails or tweak the content to better align with your subscribers' interests.

9. Improve your deliverability

If your emails aren’t reaching the inbox, they don’t stand a chance of being opened (let alone clicked through). Monitor your deliverability rate and follow best practices to guarantee better inbox placement:

  • Authenticate your sending domain
  • Clean your lists
  • Avoid old or inactive addresses
  • Never buy email lists
  • Remove unengaged subscribers
  • Validate email addresses
  • Be consistent with your sending volume and frequency

Improve your email sending with CTOR

SendGrid delivery expert Seth Charles put it well when he said, “Email marketing revenue is not a volume-based metric; it’s a value-based metric.”

This type of thinking is important when fostering a strong relationship with your customer. How can you deliver your customer value through email? Once campaigns go out, tracking your CTOR is a great way to see how you’re doing.

For more on how to optimize your email sending, check out our 4th Quarter Email Playbook, which is full of resources to make sure you create your best email campaigns to date—no matter what time of year it is!

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