How to Calculate
The formula is simple:
Open Rate = (Unique Opens / Emails Delivered) x 100
If you send 10,000 emails, 300 bounce, and 2,425 unique recipients open the message, your open rate is 2,425 / 9,700 = 25%.
Most email platforms calculate this automatically. "Unique opens" counts each recipient only once, even if they open the email five times. Some platforms also report "total opens" which counts every single open event.
Industry Benchmarks
Average open rates vary significantly by industry and list quality:
- Overall average: roughly 20-25% across industries
- B2B / professional services: 22-28%
- E-commerce / retail: 15-20%
- Media / publishing: 25-35%
- Nonprofits: 25-30%
Don't obsess over matching someone else's numbers. Your own trend line matters more. A consistent 18% that holds steady is healthier than a 30% that's dropping every month.
Why Accuracy Is Tricky
Open tracking works by embedding a tiny invisible image (a tracking pixel) in the email. When the recipient's email client loads that image, it registers as an "open." But there are a couple of problems:
- Image blocking: If a recipient's email client blocks images by default, the open won't be recorded even though they read the message. This means your real open rate is almost certainly higher than what's reported.
- Apple Mail Privacy Protection: Since iOS 15 (September 2021), Apple pre-fetches tracking pixels for Apple Mail users, inflating open counts. If a big chunk of your audience uses Apple devices, your reported open rate might be 10-15 percentage points higher than reality.
Because of these issues, many marketers now treat open rate as a directional metric rather than an exact measurement. Click rate and conversion rate are more reliable for gauging true engagement.
How to Improve Your Open Rate
Your open rate is primarily driven by three factors: who you're sending to, what your subject line says, and when you send.
Clean Your List Regularly
Remove inactive subscribers who haven't opened in 90+ days. A smaller, engaged list will always outperform a bloated one full of dead addresses. Run a re-engagement campaign first, then cut the non-responders.
Write Better Subject Lines
This is the single biggest lever you have. Keep them under 50 characters, create curiosity or urgency (without being clickbaity), and personalize when possible. A/B test two subject lines on 10-20% of your list, then send the winner to the rest.
Optimize Send Timing
Tuesday through Thursday between 9-11 AM in the recipient's time zone tends to perform best for B2B. B2C often sees good results on weekends. But these are starting points -- test what works for your specific audience.
Nail Your Preheader Text
The preheader (preview text) appears right next to the subject line in most inboxes. Don't waste it on "View in browser" or let it default to your navigation links. Write it as a companion to your subject line that adds context and pulls people in.
Build Sender Recognition
People open emails from senders they trust. Use a consistent From name, send on a predictable schedule, and make sure every email delivers value. Over time, subscribers will open out of habit.
Open Rate vs. Other Metrics
Open rate tells you whether your subject line and sender reputation are doing their job. It doesn't tell you whether the content inside was any good. For that, look at click-through rate (did they engage with the content?), conversion rate (did they take the action you wanted?), and unsubscribe rate (did they actively disengage?).
Think of it as a funnel: open rate is the top, click rate is the middle, and conversion rate is the bottom. All three matter, but optimizing only for opens can lead you astray -- clickbait subject lines boost opens while tanking everything else.