What Is Email Open Rate? How to Calculate and Improve It

What Is an Email Open Rate?

An email open rate is the share of delivered emails that people open, shown as a percentage. If you deliver 1,000 emails and 300 people open them, your open rate is 30%. It tells you how well your sender name, subject line and timing persuaded people to look.

Open rate measures the first step of an email’s journey. It does not show whether people read, clicked or bought. Our explainer on email marketing covers how campaigns work from start to finish.

Almost every email platform reports open rate automatically. Understanding how it is measured, and where it falls short, helps you read it correctly.

How Do You Calculate Open Rate?

Divide unique opens by emails delivered, then multiply by 100.

The formula is: Open rate = (unique opens ÷ emails delivered) × 100.

• Unique opens count each person once, even if they open the email several times.
• Emails delivered are the emails sent minus those that bounced.

Here is a made-up example. You send 5,000 emails and 200 bounce, so 4,800 are delivered. If 1,440 people open the email, your open rate is 1,440 ÷ 4,800 × 100 = 30%.

Some platforms also report total opens, which count repeat opens by the same person. Total opens can show strong interest in one email, but unique opens are better for comparing campaigns.

How Is an Email Open Tracked?

Most platforms detect an open with a tiny invisible image, often called a tracking pixel, hidden in the email.

When the email loads its images, the pixel is downloaded from the sender’s server, and the platform records an open. This method has always had blind spots:

• Images turned off: if someone reads the email with images blocked, no open is counted.
• Plain-text views: text-only versions cannot load a pixel.
• Automatic image loading: some systems load images without a person reading, which can count false opens.

The last point has become the biggest issue, because of a major change by Apple.

How Does Apple Mail Privacy Protection Affect Open Rates?

Apple Mail Privacy Protection, introduced in 2021, preloads email content, which can make emails look opened even when nobody read them.

When an Apple Mail user turns on the feature, Apple downloads the email’s images, including tracking pixels, through its own servers. The sender’s platform often records an open whether or not the person ever looked. Mailchimp notes that privacy features such as Mail Privacy Protection can affect the accuracy of open rates.¹

The result is inflated open rates for lists with many Apple Mail users. It also weakens tactics that rely on opens, such as sending to people who opened recently or picking the winning subject line by opens alone.

What to Do About It

• Treat open rate as a rough signal, best for spotting big changes rather than small differences.
• Judge success by clicks, replies and conversions, which privacy features do not fake.
• Use click-based engagement to decide who counts as an active subscriber.
• Check whether your platform flags machine opens, and exclude them in reports where possible.

What Is a Good Email Open Rate?

Mailchimp’s published benchmarks put the average open rate across all industries at about 35.6%, with an average click rate of about 2.6%.¹ Those figures reflect data available as of December 2023 and include the effect of privacy features.

Averages vary a lot by industry, list size and type of email. Small, engaged lists of people who asked for your emails often see higher rates. Large promotional lists usually see lower ones.

Business-to-business emails sent to work addresses can behave differently again, because company filters and busy inboxes affect what gets seen.

The most useful benchmark is your own history. Compare each campaign with your recent average, and watch the trend over months rather than reacting to a single send.

What Affects Your Open Rate?

Several factors decide whether an email is even seen, and then whether it gets opened.

• Deliverability: an email that lands in spam is rarely opened. Authentication and a good sender reputation help it reach the inbox.
• Sender name: people open emails from names they recognize and trust.
• Subject line: the main hook. Clear, specific and honest subject lines usually beat vague or hyped ones.
• Preview text: the short line shown after the subject in many inboxes. Use it to add a second reason to open.
• Timing: the day and hour can matter, depending on your audience’s routine.
• List quality: old, purchased or unengaged addresses drag the rate down and can harm deliverability.
• Relevance: emails that match what subscribers signed up for get opened more.

How Do Deliverability Rules Affect Opens?

Since 2024, Google and Yahoo require bulk senders to meet stricter rules, and emails that fall short are more likely to be filtered or rejected.

Google’s sender guidelines ask anyone sending large volumes to authenticate their mail with SPF, DKIM and DMARC, offer one-click unsubscribe and keep reported spam rates low, ideally below 0.1% and never reaching 0.3%.² Yahoo has set out similar expectations for bulk senders.⁴

These rules protect inboxes, and they reward good practice. Senders who authenticate properly, honor unsubscribes quickly and send wanted emails tend to see better inbox placement, which lifts opens naturally.

US law also sets basic rules. The FTC’s CAN-SPAM guidance requires honest subject lines, accurate sender details, a valid postal address and a working opt-out honored within 10 business days.³

How Do You Write Subject Lines That Get Opened?

A good subject line tells the reader exactly what is inside and why it matters to them, in as few words as possible.

• Be specific. Name the benefit or the topic, such as “Your May bill is ready” or “5 easy dinners under 30 minutes.”
• Keep it short. Many phones show only the first 30 to 40 characters, so put the important words first.
• Match the email. A subject line that over-promises wins one open and loses trust for the next ten.
• Use numbers and names carefully. Numbers set clear expectations; personalization helps only when it feels natural.
• Avoid spammy patterns. All capitals, many exclamation marks and pushy phrases can hurt both trust and inbox placement.
• Pair it with preview text. The subject hooks attention; the preview adds the second reason to open.

When you test subject lines, send each version to a random slice of the list and compare clicks as well as opens. Because privacy features inflate opens, a version that wins on opens alone may not be the real winner.

Why Do Open Rates Differ by Type of Email?

People treat different kinds of email very differently, so one average never fits them all.

• Transactional emails, such as receipts, password resets and delivery updates, tend to be opened the most, because people expect and need them.
• Welcome emails usually perform well, because the subscriber has just signed up and is paying attention.
• Newsletters depend heavily on how useful and regular they are.
• Promotional emails often see lower rates, especially when sent frequently.
• Re-engagement emails to inactive subscribers usually see the lowest rates, which is expected.

Compare like with like. Judge each newsletter against previous newsletters, and each promotion against previous promotions.

How Can You Improve Your Open Rate?

Most gains come from sending the right email to the right people with an honest, specific subject line.

1. Clean your list. Remove addresses that bounce and people who have not engaged in many months, after a final re-engagement email.
2. Authenticate your domain. Set up SPF, DKIM and DMARC so inbox providers trust your mail.²
3. Use a recognizable sender name, such as a person’s name plus your brand.
4. Write specific subject lines that say what is inside. “3 ways to cut your energy bill this winter” beats “Our latest newsletter.”
5. Use preview text deliberately instead of letting it show “View this email in your browser.”
6. Segment your list so each group gets emails that match their interests.
7. Test one change at a time, such as subject line or send time, and judge the result by clicks as well as opens.
8. Keep promises. Send what people signed up for, at the frequency you said.

Which Email Metrics Matter More Than Open Rate?

Because opens are now less reliable, most marketers lean on metrics that show real action.

Conversion rate is usually the number that matters most to the business. Our explainer on conversion rate shows how to measure it across channels.

How Often Should You Check Your Open Rate?

Look at each campaign a day or two after sending, then review trends monthly.

Most opens happen within the first 24 to 48 hours, so checking too early gives an incomplete number. A monthly review smooths out one-off swings caused by holidays, news events or an unusual subject line.

Track a few numbers side by side in a simple spreadsheet: open rate, click rate, unsubscribes and sales for each email. Patterns appear quickly. You may notice that certain topics, days or formats consistently do better, which tells you what to send more of.

A Worked Example

Here is a made-up example of a newsletter improving its results.

A small online bookshop sends a weekly email to a list of 8,000 people. Its open rate is 22% and its click rate is 1.1%. About 1,500 addresses have not clicked in a year.

The shop sends those inactive subscribers a final “still want to hear from us?” email and removes those who do not respond. It sets up domain authentication, changes the sender name from “Newsletter” to the owner’s name plus the shop, and starts writing subject lines that name the books inside.

Over the next two months, the list shrinks to 6,900, but the open rate rises to 31% and the click rate to 2.4%. More importantly, weekly sales from the email grow, because the remaining subscribers are the ones who actually read.

Common Open Rate Mistakes

A few habits make open rate misleading or drag it down.

• Celebrating opens alone, without checking clicks and sales.
• Comparing with averages from other industries instead of your own history.
• Buying email lists, which harms deliverability and is likely to break platform rules.
• Using misleading subject lines, which can win a one-off open but lose trust, and may break CAN-SPAM.³
• Never cleaning the list, so inactive addresses pile up and drag down results.
• Testing too many things at once, so you cannot tell what made the difference.

Key Terms Explained

These words appear in nearly every email report.

• Unique open: one open per recipient, however many times they view the email.
• Tracking pixel: a tiny hidden image used to detect when an email is opened.
• Deliverability: how reliably your emails reach inboxes rather than spam folders.
• Preview text: the short line shown next to or below the subject in many inboxes.
• Authentication (SPF, DKIM, DMARC): technical records that prove an email really comes from your domain.
• Click-to-open rate: the share of people who opened an email and then clicked a link.

The Bottom Line

Open rate shows how many delivered emails get opened, but privacy features now inflate it, so treat it as a rough signal rather than proof of success. Calculate it as unique opens divided by delivered emails, compare it with your own past results and judge campaigns mainly by clicks and conversions. Clean lists, proper authentication and honest subject lines lift every number. For more, browse our marketing explainers.

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