Learn the Right Way to Calculate Email Open Rate

On February 13, 2023
8min read
Denys Kontorskyy Technical Content Writer @Mailtrap

In the blog post on Email Marketing Metrics, we broke down key performance indicators by their priority. Of more than 20 metrics, the open rate was highlighted as a pivotal one. It is a foundation for building analytics for your email campaigns. On the one hand, the email open rate is easy to calculate and work with. However, the metric has its own quirks that you should explore in detail. In this article, we highlight essential information about the email open rate and discuss them below.

What is an email open rate for?

The open rate shows how many recipients of the entire mail list opened the email campaign. This metric defines the success or failure of the campaign. If the rate is good enough, you can go deeper and analyze other consequent metrics to optimize your emails. If the open rate is low, your key task is to increase it. 

Email open rate calculation formula

Formula #1

Open rate = (total unique opens ÷ total recipients) x 100

You need two variables to calculate the open rate:

  • Total recipients – how many email addresses are on your mailing list
  • Total unique opens – how many recipients opened your email 

Divide the number of emails opened by the number of total recipients and multiply the outcome by 100. 

Bear in mind that you need the number of unique opens only. If recipients open the same email twice or more, they only count as one unique open.

Formula #2

Open rate = (total unique opens ÷ (total recipients – bounced emails)) x 100

Some companies use a more advanced formula for open rate calculation with three variables:

  • Total recipients – how many email addresses are on your mailing list
  • Total unique opens – how many recipients opened your email 
  • Bounced emails – how many emails failed to reach the inbox

For example, of 1K total emails sent, 15 bounced, including soft and hard bounces. This means that 15 recipients did not open them due to a technical issue rather than poor engagement of the email campaign. This alternative formula provides more accuracy of the open rate with a focus on the number of people that engaged with the email.

Read more about managing your bounce rate

How do you calculate the email open rate for multiple campaigns?

Let’s say your last three email campaigns had the following open rates:

  • Campaign A: 16% 
  • Campaign B: 20%
  • Campaign C: 22% 

Add them all together and divide that by three:

(16 + 20 + 22) ÷ 3 = 19.3%

This is the average open rate for your email campaigns.

What is the difference between the open rate and the click-to-open rate?

The open rate mostly rests on the quality of subject lines and pre-inbox optimization. The click rate shows whether the email design panned out. The click-to-open rate (CTOR) blends the open rate and email click rate into a single metric that measures the relevance and effectiveness of the email content. 

With the CTOR, you get an idea of how many recipients opened the email and clicked the CTA in it. Here is the formula to calculate the click-to-open rate:

Click-to-open rate = (total unique clicks ÷ total unique opens) x 100

For example, your email campaign was opened by 150 recipients, and only 42 of them clicked the CTA link. As a result, your click-to-open rate is 0.28 or 28%, which is good enough. According to different research, the benchmark for the CTOR metric is 20-30%

Ways to track email opens

Email service providers mainly track email opens via tracking pixels and trackable links. There is also a read-receipt tracking mechanism that is rarely used nowadays. We explored each option in How Email Tracking Works. Here is a short summary. 

Tracking pixels

A tracking pixel is a piece of HTML code embedded in the email. Each tracking pixel is assigned a unique tracking number. When the recipient loads the email, the tracking number marks it as read. This is the most reliable way of tracking opens, which is used by many marketing platforms and email services, such as MailerLite or Amazon SES. 

However, this performance indicator is not 100% accurate. The tracking pixel won’t load and report the open if the recipient’s email client has images and HTML turned off. Different marketing services use their own approaches to reduce this margin of error. For example, MailChimp factors in click-through rate (CTR) with open rates.

Trackable links

A trackable link is a link generated with the use of tracking software and inserted into email content. So, trackable links are visible to the email recipients, whereas tracking pixels are not. When the recipient clicks on this link, you get information about who opened the email and when. Trackable links are mainly created using UTM parameters, which allow you to track a wide range of user engagement data. Here is an example of a trackable link:


The problem is that a recipient can open the email but ignore the link. In this case, the email won’t be marked as opened. 

Read receipts

It is also worth mentioning that read receipts are a way to learn whether an email has been opened. They work as follows:

  • a sender’s email client sends a receipt request along with an email
  • once notified of the request, the recipient can either consent or decline to send a read receipt

Truth be told, this tracking option could be more reliable. If the recipient’s email client does not allow read receipts in the settings, you’ll never know whether the email has been opened. Besides, the read receipts mechanism mostly works if the sender and recipient use the same email client. 

Is my open rate good or not?

In addition to the quality of the email content and email list, the following factors will contribute to an excellent open rate:

  • Email type – the open rate of transactional emails is usually two or three times more than marketing emails.
  • Industry – open rates in different industries can vary a lot. 
  • Sending date and time – to get the highest open rate, it’s crucial to identify the perfect day and time for launching an email campaign. 
  • Target region – open rates in different regions can vary a lot. 
  • Recipient’s device – open rates from mobile devices keep growing yearly.

All these factors matter and need to be considered in your marketing strategy. But what is a good email open rate on average? Take a look at the following industry average benchmarks based on the many years of experience of the Mailtrap marketing team:

As you can see, the email marketing benchmarks are significantly lower, so improving them for a better conversion rate is a non-stop process.

How to improve my email open rate?

The recipient often thinks about two things before opening an email: subject line and sender name. So, if you have a low open rate and want to increase it, make sure to optimize both of them.

Use a proper sender name

People prefer to interact with people. That’s why an email message from a specific contact person has more credibility with recipients. So, instead of using a generic email address, such as “Marketing crew” or “Support Team”, opt for something like “Jane from [Company name]”.

General email addresses reduce the open rate, while personal email addresses can lift it by 15+%.

Another valuable tip for increasing the credibility of an email sender is to use the Brand Indicator for Message Identification or BIMI. This DNS TXT record allows brands to display their logo next to each email in the inbox. Here is how emails from different brands may look in an inbox before and after the BIMI implementation:

For more on how to join the BIMI club, read our blog post Do Your Emails Need BIMI?

Fine-tune the subject line

The subject line of your email campaign must be:

  • Concise – email subject lines with up to 10 words have higher open rates and tend to show the best results. Keep in mind that your recipients will often open emails from mobile devices as well. That’s why the optimum length of the subject line is up to 90 characters.
  • Relevant – if a recipient ignored your previous emails about discount offers, he or she is unlikely to open them this time. In this case, it’s better to segment your email list. This will allow you to increase engagement and keep the number of subscribers from dropping. 
  • Apprehensible – let recipients understand right in the subject line what you want them to read. 
  • Catchy – when a recipient scans his or her inbox,  the average email has a few seconds (three or four) to catch the eye. So, the open rate of your email marketing campaign depends on whether the subject line manages or fails to draw the recipient’s attention. 
  • Personalized – subject lines containing a recipient’s name usually show good open rates. However, adding “Hey [subscriber’s name]” to the subject line is unlikely to raise your rates significantly. Be creative, and you’ll be able to take the biscuit.

Besides the mentioned best practices, you should also avoid the following in your subject lines:

  • Spam trigger words such as No cost, One-of-a-kind deal, Risk-free, and many, many more.
  • Words typed with Caps Lock jammed 
  • !!!!!!!!! or $$$$$$

It’s equally important to have a reliable email-sending solution that can help with high deliverability rates and increase the chances of your emails being opened. One such solution is the Mailtrap Email Delivery Platform, which is comprised of Email Sending and Email Testing. 

Email Sending is designed to deliver high email deliverability rates, thus providing a reliable email infrastructure for sending and monitoring your emails’ performance. There are two options for sending: SMTP for easy integration with any application and API for more flexibility.

One of the critical features of Email Sending is its robust monitoring system that tracks your Unique Ope, Click, Bounce, and Spam rates and provides detailed statistics. The system is equipped with a critical alert system that can notify you if there is an issue with any of the rates.

Furthermore, to ensure the best performance of your emails, a range of monitoring tools include helicopter-view dashboards and drill-down reports with statistics on various mailbox providers such as Gmail, Microsoft 365, Outlook, Yahoo, and G.Workspace.

You can also view detailed statistics and email categories and access up to 60 days of email logs.

Besides having access to the general performance of your Open Rates, you can get more information on each sent message via email logs. For example, the detailed Event History shows you the actual time when your email was delivered and opened, allowing you to understand your email performance more deeply. 

This information can help you make informed decisions about your email strategy, such as adjusting your sending schedule to target your subscribers when they are most active or making changes to your email content to improve engagement.

How to test my emails for a better open rate?

Each email goes through authentication mechanisms and spam filters implemented on SMTP and IMAP (or POP3) servers. So, always test your email campaigns before sending them and aim at having your emails successfully pass the following:

Email sending capability of your app – send a test email for this. This is where Mailtrap Email Testing can be helpful. Email Testing offers a comprehensive solution for inspecting and debugging emails in various environments, such as staging, development, and QA, without annoying your recipients with test emails.

You can quickly check the compatibility of your email templates with popular mailbox providers, assess their spam scores, check if you’re on any blacklist reports, and validate your email’s HTML/CSS. If you need even more power, Mailtrap’s Email Testing API enables you to automate your testing flows and further streamline your work.

SMTP relay – whether your SMTP server can route emails to the proper destination SMTP server. You can use Telnet or one of the web-based tools such as MX toolbox. Check out our blog post on Test SMTP Relay for more information.

Email for spam – run tests for deliverability, spam, and email address validity. There are many online tools for this, which we introduced in the Email Testing Checklist.

Email content – preview your email, test its HTML and body copy, and the subject line. This is a final flourish, after which you can click the Send button.

After reading this article, we hope you’re better equipped to calculate and monitor your email open rates more effectively, which will ultimately lead to more impactful email marketing campaigns! 

Article by Denys Kontorskyy Technical Content Writer @Mailtrap

I am an experienced Technical Content Writer specializing in email infrastructure, offering insights on sending, testing, and optimizing emails. I also have a strong interest in product marketing, creating engaging content that drives audience engagement and supports business growth.