Definition: Open Rate

Open Rate is the percentage of people who were sent an email who opened it. It is one of the core email marketing metrics, along with Delivery Rate, CTOR, and Conversion Rate. It is occasionally shortened to just OR – but only by email marketing professionals.

Open Rate is an odd email marketing metric, as it is not used to measure how good the content of an email is, but rather the meta-variables around it, such as:

  • Subject line
  • Preview Snippet (the small part of an email you can see in your inbox)
  • The Date & Time the email was sent.

It can also help measure the general loyalty and interest of the users being sent the email.



Open Rate Definition

Open Rate is defined as the percentage of people who opened an email out of all the people who had that email delivered to them.

Please note the use of “delivered”. While the definition of what counts as a “delivered email” varies slightly between email platforms, it does not include emails that have bounced or were not accepted at all. This is important to note as Open Rate is not the percentage of people who opened an email out of the number of people you sent an email, but rather out of the number of people who “received” that email.


Open Rate Formula

The Open Rate equation is:

Open Rate Formula for our Open Rate calculatorClick to enlarge

Open Rate = (Opened x 100) ÷ Delivered


Average Open Rate

The general consensus is that Open Rates generally hover between 15%-25%.

If you are getting an open rate below 15% then you should start testing your subject line, preview snippet, and the time (and day) you send your email. Only do one of these things at a time so you can try to work out whether or not it is having a positive effect.

If you are getting above 25% then good work, keep it up.


Technical Information

There are a few important things to note about Open Rate:

  1. Each email address that receives an email can only record one “open”. This means that even if someone receives an email, opens it, and then marks it as unread and opens it again – it will still only count as one open.
  2. What counts as a delivered email varies depending on the email platform. The general rule is that an email is counted as delivered once it has been accepted by the receiving server from the delivering email platform – which means that only emails that don’t bounce are included. However, whether or not an email getting caught by a spam or junk mail filter counts as a bounce is not consistently agreed upon. This means that for some email platforms an email still counts as delivered even if it is quarantined as spam and never seen by a user at all.
  3. Some email software (such as Outlook) Previews an email automatically both when the email software is launched, and when an email is clicked on (even if it is immediately deleted). These “previews” are generally counted as opens, which means that the number of opens is generally inflated (although there is no consensus on how much it is inflated by).
  4. Since iOS15 Apple Mail will automatically open all emails, with the intention of making tracking harder.


7 Key Points About Open Rate

  1. Getting people to open emails is the 2nd obstacle to overcome in email marketing (after getting past junk filters in the first place).
  2. Open Rate is *always* inaccurate. Email Platforms can’t track opens directly. Instead, they insert a tiny image into emails & count only when it loads. HOWEVER most email providers don’t allow images by default, so won’t count.
  3. To optimise your open rate take a look at:
    🤵 Who your email is from
    ⁉️ Your email subject line
    🔎 Your preview snippet
    🕒 When you send your email
    📅 How often you send emails
    ÷ Segmenting your list
  4. Adding images to your email will increase your open rate. Opens are tracked by a pixel loading. No one will “download all images” if there are no images to see, and so the tracking pixel won’t be loaded either.
  5. Even though Open Rate is a deeply flawed metric, it’s still useful in the short run. The fact that it is deeply flawed makes it less useful for long-term analysis though as those flaws are inconsistent. In practical terms, this means that Month-on-Month analysis is more valuable than Year-on-Year.
  6. If someone has an inbox that loads previews of emails – that still counts as an open (if they allow images).
  7. If you optimise your open rate, you will likely see your CTOR drop (more opens without more clicks makes for a worse CTOR). Optimise both together (and the landing page too to keep your conversion rate up).



Open Rate Definition

Glossary Index