What is an open rate? Email Marketing 101

Written by Shaun Chojnacki | Apr 25, '25

Email marketing is a crucial element of any digital marketing campaign. It can drive traffic to your website, increase engagement with your brand, and ultimately lead to more sales. But, as with any marketing tactic, it's essential to measure the effectiveness of your email campaigns.

One metric often used is email open rates. In this article, we'll examine email open rates, how they're calculated, and what you should use them for.

What is an open rate?

First, let's define what an open rate is. An open rate is a metric used in email marketing that measures the number of times a recipient opens an email. This is usually expressed as a percentage of the total number of emails sent.

For example, if you send 100 emails and 20 of them are people who opened, your open rate would be 20%.

BigCommerce says:

An Open Rate is an email marketing metric that measures the percentage rate at which emails are opened. Though it is a general indicator of subject line effectiveness, it can be a misleading metric for online marketers.

It's important to note that there are better metrics than an open rate for measuring the effectiveness of an email campaign. Andrew Kordek, iPost, points out that an open rate doesn't necessarily mean someone actually read or engaged with your email.

Instead, it simply means that the email was rendered, and an invisible pixel was fired. Therefore, it's not a metric that should be used in isolation.

What is a good open rate?

According to Mailchimp, good open rates vary by industry and by percentage. In their Email Marketing Statistics and Benchmarks Report, results vary from 15% to 27%.

Hubspot claims the average open rate is 20.94%. They also say the results for your organization, however, will depend on your list's health, the quality of your subject line, and the average benchmark for your industry.

What are open rates used for?

So, what should you use open rates for? Kordek suggests that open rates can help identify potential deliverability problems. If your open rates are consistently low, it may indicate that your emails are getting caught in spam filters or not reaching your subscribers' inboxes. By breaking down your open rates by your top five or ten ISPs and looking at trends over time, you can identify whether there is an issue and take steps to address it.

It's also worth noting that open rates can vary depending on your industry and the type of email you're sending.

For example, if you're in the retail industry and sending promotional emails, you may be seeing higher open rates than if you're in the financial services industry and sending informational emails.

Therefore, it's only sometimes useful to compare your open rates to industry benchmarks, as these can be skewed by the type of email being sent.

Calculating Open Rates

When it comes to calculating open rates, different methods can be used. Kordek notes that he's seen open rates calculated as total opens over delivered, total opens over sends, unique open over sends, and unique open over delivered.

This means that it's essential to understand how your email service provider calculates open rates so that you can compare apples to apples.

What Can Open Rates Tell You?

In the post, Email Open Rate Meaning – Why You Shouldn’t Worry, Cameron Kane, CEO at iPost, elaborates on what you can truly gauge from analyzing open rates.

In the post, he mentions that:

Open rates can tell you:

The effectiveness of subject line (good or bad)

The quality of your list (low or high)

The frequency and/or cadence of your sends (too many, too few, just right)

How well you’re segmenting

The best days and times for sending marketing emails

Conclusion

In conclusion, email open rates can be a useful metric for identifying potential deliverability problems, but they shouldn't be used in isolation to measure the effectiveness of an email campaign.

It's essential to understand how open rates are calculated and to be aware that they can vary depending on the industry and the type of email being sent. This must be understood before attempting to improve open rates.

Ultimately, a successful email campaign should be measured by a range of metrics, including click-through rates, conversion rates, and revenue generated.

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