What is an open rate?
The open rate shows what percentage of recipients open your emails out of the total number of emails that are actually delivered to their inboxes. You calculate the rate by dividing the number of unique opens by the number of emails delivered and multiplying by 100. In other words, you get a percentage that indicates how effectively your email piques curiosity right in the inbox.
The tracking itself typically occurs via a small, invisible image file—a so-called tracking pixel—that is activated when the recipient opens the email. When the image is loaded, the system registers the opening. This makes the rate sensitive to changes in recipients’ technological environments, because, for example, Apple’s Mail Privacy Protection (MPP) can automatically load these images and thus artificially inflate the numbers. Therefore, you should always interpret open rates with caution and view them as an indication, not an accurate measure of actual reading.
The open rate is closely tied to the first impression your email makes in the inbox. The sender’s name, subject line, and timing are crucial in determining whether the recipient will even choose to open the email. This also means that developing your email strategy is very similar to crafting ad copy for Google Ads or your organic social media posts, where small linguistic and visual variations can make a big difference in engagement.
How do you use your knowledge of open rates?
You use the open rate as an indicator of how well your emails are performing in the first phase of the recipient journey. When you see a drop in the rate, it suggests challenges with either deliverability, sender identity, or subject line relevance. Conversely, when the rate increases, it shows that your changes are reaching your target audience more effectively.
The most important thing is not to interpret the open rate in isolation. The open rate tells you nothing about what happens after the email is opened. That’s why many email marketers use it in conjunction with click data and conversion metrics. Just as you evaluate both impressions and clicks in SEO to understand user behavior, the open rate helps you assess whether your email is even making it into the inbox.
Here's an example of how you can use the numbers:
Why is the open rate important?
The open rate serves as an early indicator of performance. It helps you understand whether your campaigns are even managing to capture people’s attention. Although you shouldn’t use it as a KPI for actual engagement, you can track its trends over time to measure improvements in branding, sender trust, and deliverability.
For those of you who work with marketing automation, the open rate is also important for adjusting workflows. If welcome emails and newsletters have significantly different open rates, it indicates that triggers or the timing of the send are factors. In this context, optimizing email open rates is similar to fine-tuning CPC bids in paid campaigns—it’s not about the number itself, but about the impact of each adjustment.
In addition, a stable and reliable open rate helps strengthen your brand’s presence in the inbox. Emails that are opened repeatedly build brand recognition, and over time, you can use this insight to plan how your customers experience your communications across channels—from email to social media and on to your website.
What types and varieties are available?
There are several related metrics that help you understand user behavior in greater detail:
- Open Rate (OR): The classic metric based on all emails delivered.
- Click-to-Open Rate (CTOR): The percentage of users who both open and click—a direct measure of the content's relevance.
- Click-Through Rate (CTR): The number of clicks relative to the number of emails delivered or opened, depending on the measurement method. It is often used to link opens to actual actions.
While the open rate measures curiosity, CTOR indicates the quality of the content itself. If you see a high CTOR but a low OR, it means your content is performing well—but fewer people are seeing it. It’s similar to a social media post that performs well in terms of engagement but poorly in terms of reach: your content has potential, but it needs better visibility to realize that potential.
How do you work with open rates in practice?
You measure and track the open rate in your email marketing tool, such as HubSpot, MailerLite, or Campaign Monitor. Here, you can see how open rates change over time and compare your numbers to industry averages. Typically, an open rate above 30% is considered solid, 45–50% is considered strong, and above 50% is considered exceptional. However, the exact levels vary across industries such as nonprofit, e-commerce, or software.
In practice, you work with the open rate when you test different subject lines, segment audiences, or schedule send times. For example, you can send A/B tests of subject lines to small samples of recipients and use the results to choose the version that performs best. You can also use your knowledge from SEO or social media marketing to identify the words and angles that drive clicks and recognize patterns that also apply to email communication.
What should you keep in mind?
Technological and behavioral factors are influencing open rates more than ever. Privacy tools, such as MPP, can skew the numbers because they automatically track opens. Therefore, it’s a good idea to view the open rate as a relative metric and focus on trends rather than the absolute number.
Furthermore, you shouldn’t overestimate the open rate as an indicator of success. A high open rate is only valuable if it leads to clicks and action. The same applies to any marketing channel—you get the most out of your data when you view it in context. By combining the open rate with click data, conversion rates, and user behavior on the website, you’ll gain a comprehensive picture of how effectively your communication is working for you across digital channels.
