Email open rate is one of the oldest numbers in email marketing, and one of the most misunderstood. People ask what a good open rate is, how to calculate it and how to raise it. This guide answers all three honestly. It explains how open rate is measured, why the number has become less reliable since mail apps began loading images automatically, why we do not quote a single benchmark and what to track instead, and gives practical ways to improve engagement that do not rely on a figure you cannot trust.
What is email open rate?
Open rate is the share of delivered emails that were opened. A sending platform measures an open by embedding a tiny, invisible image in the HTML message, often called a tracking pixel. When the reader's mail app loads the image from the sender's server, the platform records an open. If images are not loaded, no open is recorded, even when the person read the message.
That means open rate is a measurement of image loads, and not of people reading. For years the two were close enough. Today they often are not.
How to calculate email open rate
The usual formula is:
Open rate = (unique opens / emails delivered) x 100
Three details change the answer.
- Delivered, not sent. Use the number of messages that were accepted by the receiving server, so that bounces do not lower the rate. Some tools use "sent" instead, so compare like with like.
- Unique, not total. A person who opens the message five times counts once in unique opens. Total opens can exceed 100 per cent of the list.
- The time window. Opens keep arriving for days. A rate measured after one hour differs from one measured after a week.
Example: you deliver 10,000 messages, and the platform records 2,500 unique opens. The open rate is 2,500 divided by 10,000, which is 25 per cent. Your platform's email analytics shows these figures per campaign.
What is a good email open rate?
This is the question behind most searches, and the honest answer is that no single number is reliable. We do not quote one for these reasons.
- Benchmarks vary widely by source. Studies published by marketing platforms report different averages, because they measure different senders, in different industries, with different definitions of an open and different handling of automatic opens.
- Industry and list type matter. A newsletter to people who asked for it, a message to customers and a cold outreach campaign behave very differently.
- The measurement itself changed. Automatic image loading raises recorded opens, so older benchmarks and newer ones are not comparable.
- Your own history is the best baseline. A rate that is stable for your audience, with the same measurement method, is more useful than someone else's average.
If you need a reference, look at the published benchmark reports of a source you trust, check how it defines an open and note the date. Treat the figure as a rough guide. Use your own trend as the real target.
Why open rates are less reliable than they were
Mail privacy features
Some mail apps now protect their users' privacy by downloading images in advance, through a proxy, whether or not the person opens the message. Apple introduced Mail Privacy Protection in 2021, and it caused many recorded opens to be machine opens that do not reflect reading. The effects are that open rates look higher than before, that open time and location data are unreliable for those readers and that "opened" can no longer be treated as proof of interest.
Image blocking
In the opposite direction, readers who block images by default are not counted when they read. Plain-text emails have no pixel at all.
Security scanners
Corporate security tools sometimes open messages and links to check for threats. These automatic opens and clicks appear in your reports as engagement. Look for patterns such as many opens in the same second after sending.
Gmail image caching
Gmail serves images through its own proxy, which can hide some details such as the reader's location, though a first open is still generally recorded.
The result is that open rate is useful as a rough indicator of whether your subject line and sender name worked, and poor as a measure of success on its own.
Better measures than open rate
- Click-through rate. Clicks on links show intent. Be aware of scanner clicks, but they are rarer and easier to filter than opens.
- Click-to-open and conversion rates: what happens after the click, on your site.
- Replies. A reply is a clear positive signal, and mailbox providers value real conversations. See the no-reply email address guide.
- Unsubscribe and spam complaint rates. They tell you whether your list wants your mail. Keep complaints very low.
- Bounce rate. A high rate signals a list quality problem. See bounce codes explained.
- Placement tests. Seed tests and tools such as Google Postmaster Tools show whether mail lands in the inbox. See Google Postmaster Tools setup.
- Revenue or goal completions per message. The measure that matters most for the business.
How to improve engagement with your emails
- Get delivered first. If messages land in spam, nobody opens them. Authenticate your domain, keep your list clean and watch your reputation. See email reputation and authenticating your domain.
- Use a recognisable sender name. People open mail from names they know. A person plus a company name often works well.
- Write a clear subject line. Say what is inside, in plain words, and avoid misleading hooks. Test two versions on a small part of the list.
- Use preview text. The short line shown after the subject in many inboxes is a second chance to explain the value.
- Send to people who want the mail. A confirmed sign-up and relevant content do more than any trick. See double opt-in.
- Segment. Send different content to different groups, based on what they signed up for or bought.
- Choose a consistent schedule. Readers learn when to expect you. Test send times, but do not expect a magic hour.
- Clean out the unengaged. Sunset subscribers who have not engaged for a long time, after a re-confirmation attempt. A smaller, more engaged list usually performs better and protects your reputation.
- Keep the message light and readable. See HTML email templates for the practical rules.
- Avoid the promotions folder where you can. See the Gmail Promotions tab guide.
How to read your reports sensibly
- Compare campaigns to your own past results, using the same definition of an open.
- Look at opens together with clicks. A big jump in opens with no change in clicks suggests machine opens.
- Segment by mail provider and by app, if your platform allows. A rate that is suspiciously high for one provider may be automatic loading.
- Watch trends over weeks, not single sends.
- Do not make list-removal decisions based on opens alone, since an unrecorded read is still a read.
A note about tracking and privacy
Open tracking involves loading a remote image, which can reveal that a message was opened and some technical details. Privacy laws and mail apps treat this differently in different places. Be open about tracking in your privacy policy, and check the rules that apply to your audience. This guide is not legal advice.
Measure what matters Follow each message from delivery to click, with bounces, complaints and deferrals in one view.
References and further reading
Frequently asked questions
How do you calculate email open rate?
Divide unique opens by the number of delivered emails and multiply by 100. Use delivered and not sent, and use unique opens and not total opens.
What is a good email open rate?
There is no single reliable figure. Benchmarks differ by source, industry, list type and how automatic opens are handled. Use your own stable trend as the baseline.
Why are open rates unreliable now?
Some mail apps preload images through a proxy, such as Apple Mail Privacy Protection, security scanners open messages and some readers block images, so recorded opens no longer match reading.
What should I track instead of open rate?
Click-through and conversion rates, replies, unsubscribe and complaint rates, bounce rate, inbox placement and revenue or goals per message.
How can I improve my email open rate?
Get delivered with authentication and a clean list, use a recognisable sender name, a clear subject and preview text, segment your audience, keep a steady schedule and sunset the unengaged.