Email Deliverability

What is email open rate and how do you calculate it?

July 4, 2024
7 min.

Email open rate is one the pillar stats of any email marketing.

It tells you what percentage of recipients have opened your email.

Without the open rate, there’s no way to know exactly how successful your campaigns are.

We’ll discuss how to calculate this essential stat, answer the question of whether open rates are accurate, and discuss what factors affect it.

How to calculate open rates ➗

Email open rate is simply the number of opens divided by the number of emails sent.

The resulting percentage is your open rate.

Here’s an example:

Let’s say you sent out 125 emails and got 25 opens.

All you have to do to find your open rate is dividing 25 by 125 and voila, your open rate is 0,2 or 20%.

There’s one caveat, though…

You want to use unique opens as opposed to all opens.


Some recipients may open your email ten times, severely inflating your open rates.

So make sure to divide the number of emails sent by unique opens when calculating your open rate.

The good news is that most email-sending tools calculate your open rates for you. And they use unique opens, too!

lemlist campaign stats

Are open rates accurate? 🔍

Unfortunately, even with the best email-sending tools, some inaccuracies in open rates can occur.

This is primarily due to circumstances outside their control, such as:

  • Some spam filters open your emails to check their content. This can lead to an inflated open rate and make it seem higher than it really is.
  • Opens are often tracked by a tracking pixel or the downloading of some external content. The open isn't tracked if the recipient has blocked images or external content from their emails. This could deflate the open rate and make it seem lower than it really is.
  • If you send large emails, it may get clipped, preventing the tracking pixel from loading.  This can also deflate your open rate.
  • Apple Mail users now have the option to hide if and when they open emails through Apple’s Mail Privacy Protection. Apple Mail tends to open the emails even if the recipient doesn't. This inflates open rates.

What other factors affect open rates?

Cold emails tend to have a lower open rate.

Previous interactions with your emails increase your open rate as they indicate recipients are interested in your emails.

With cold emails, there’s often a lack of previous engagement, which makes taking care of other factors that could affect your open rate even more important.

List quality

Ensure to only send to valid emails.

Sending to unverified emails can lead to bounces or unopened emails.

An outreach tool like lemlist can automatically verify your leads’ emails:

Email deliverability

Email deliverability is a complex topic.

Most of it comes down to your sender reputation and your technical setup.

If you send a lot of spammy emails with lots of bounces and no engagement, your sender reputation will suffer.

When your sender reputation goes down, so will your deliverability.

An often overlooked part of email deliverability is email warm-up.

It's the process of gradually increasing sending volume and frequency to establish a reputation as someone who sends many emails that get engagement.

An email deliverability tool like lemwarm can automate this entire process for you so that you avoid the spam folder and land in the inbox.

But it’s not just about your reputation:

You must also have your technical bases covered.

Your technical setup requires you to authenticate your sending domain by implementing a few DNS records.

Through these records, Internet Service Providers can verify that it’s really you who’s sending email from your domain and that the emails’ content hasn’t been tampered with during transit.

Email subject line and body

Do your emails contain spammy words?

Spam filters will not hesitate to put you in the spam folder.

Use this free mini tool to audit your emails for spammy text:

Timing ⏱️

When you send your email can affect your open rate.

The effect isn't as dramatic as the other aspects above, but it's still worth considering.

When it comes to open rates for cold emails, Tuesday and Thursday morning emails tend to get read the most. The weekends are generally to be avoided.

Timing only comes into play after taking care of the other factors above, and after writing the best cold emails that you can.

Open rates still matter

Even though some factors can skew open rates...

Open rates are still an important stat for email outreach.

Without an open rate, you can’t calculate your conversion rate.

And without your conversion rate, you have no clue about your outreach ROI.

And without knowing your ROI, you have no business!

If you’re still not convinced about the importance of open rates, read: Should you care about open rates?

And if you want to know if your open rates are up to par, check out: What is a good email open rate?

Finally, here's how to improve your open rates.


What you should look at next

Send emails that actually get delivered with lemwar...