What Is Email Open Rate?
Email open rate measures the percentage of delivered emails that were opened by at least one recipient. It is reported per campaign and tells you how effective your subject line and sender name are at earning attention inside a crowded inbox.
Most email service providers (ESPs) track opens by embedding a tiny transparent image — a tracking pixel — in each email. When the recipient opens the email and their client loads images, the server logs an open event. This method is imperfect (more on that below), but it remains the industry standard.
The Email Open Rate Formula
Email Open Rate (%) = (Unique Emails Opened ÷ Emails Delivered) × 100
A few things to note:
- Use emails delivered, not emails sent. Bounced emails never reached a real inbox, so they should not count against your open rate. Your ESP calculates delivered as sent minus bounces.
- Use unique opens, not total opens. A unique open counts each subscriber once, even if they opened the same email five times. Total opens inflate the figure and are harder to benchmark against industry data.
Example: You send a campaign to 6,000 subscribers. 240 bounce. That leaves 5,760 delivered. Of those, 1,152 open the email. Your open rate = (1,152 ÷ 5,760) × 100 = 20%.
What Is a Good Email Open Rate?
Industry-wide, a 20–25% open rate is considered average. Above 30% is strong; below 15% warrants investigation. But averages mask significant variation by industry, list size, and audience type.
| Industry | Average Open Rate |
|---|---|
| Nonprofits & Charities | 28–40% |
| Government | 28–35% |
| Education | 25–32% |
| B2B / Professional Services | 20–28% |
| Retail & eCommerce | 15–22% |
| Travel & Hospitality | 18–24% |
| Media & Publishing | 20–28% |
Compare your rate against your own industry average — not the global average. A 22% open rate in eCommerce is strong; the same rate in a nonprofit newsletter is below average.
The Apple Mail Privacy Protection Problem
Since iOS 15 (2021), Apple Mail pre-fetches all email content — including tracking pixels — before the user opens the message. This triggers an "open" event even if the recipient never reads the email, inflating open rates by 15–30% on Apple-heavy lists.
Most modern ESPs now provide a "human opens" or "machine-open filtered" metric that strips Apple MPP events. Use this adjusted metric for accurate benchmarking. If your open rate jumped sharply in late 2021 without a corresponding increase in clicks, Apple MPP is likely the cause.
Why Your Open Rate Is Dropping
Common causes of declining open rates:
- List fatigue — sending too frequently causes subscribers to stop engaging without unsubscribing.
- Poor list hygiene — inactive subscribers drag down engagement and can damage your sender reputation with ISPs.
- Weak subject lines — generic, overly salesy, or misleading subject lines train subscribers to ignore your emails.
- Deliverability issues — emails landing in spam never get opened. Check your spam score and authentication (SPF, DKIM, DMARC).
- Wrong send time — Tuesday–Thursday mornings typically outperform Friday afternoons and weekends, though this varies by audience.
How to Improve Your Email Open Rate
- Write better subject lines. Test curiosity-gap, number-led, and question formats. Keep them under 50 characters for mobile. A/B test systematically — one variable per test.
- Clean your list every 3–6 months. Remove or segment subscribers who have not opened an email in 6 months. A smaller, engaged list beats a large, disengaged one.
- Segment your audience. Send content that matches each segment's interests. An e-commerce store sending shoe deals to people who only bought bags will see lower opens over time.
- Optimise your sender name. People open emails from people, not brands. "Mark from MarketingAI" outperforms "MarketingAI" for most audiences.
- Set expectations at signup. Tell new subscribers exactly what they will receive and how often. Subscribers who know what is coming engage more consistently.
Open Rate vs. Click-Through Rate
Open rate and click-through rate (CTR) measure different things. Open rate tells you whether your subject line worked. CTR tells you whether your email body and offer were compelling enough to drive action. A high open rate with a low CTR usually means your subject line is good but the email content or call-to-action is not delivering on the promise.
Track both. Set targets for each. Use our Click-Through Rate Calculator alongside the open rate calculator for a full picture of campaign health.
Related Calculators
- Email Open Rate Calculator — instant open rate from your campaign data
- Click-Through Rate Calculator — measure post-open engagement
- Email List Growth Rate Calculator — track net subscriber growth
- Marketing ROI Calculator — tie email performance to revenue