ConversionMath

Email Open Rate Calculator

Calculate your email open rate from delivered emails and unique opens — or reverse it to forecast required list size or expected opens.

Your Open Rate

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Formula Open Rate = (Unique Opens ÷ Emails Delivered) × 100

How to use this calculator

Enter the number of emails delivered (sent minus bounces) and the number of unique opens. The calculator returns your open rate as a percentage. Use the "Calculate" selector to solve instead for required list size or expected opens based on a target open rate.

What is Email Open Rate?

Open rate is the percentage of delivered emails that were opened. It's one of the primary indicators of email campaign performance, reflecting the strength of your subject line, sender name, send time, and sender reputation. Historically open rate was considered a reliable engagement metric, but privacy features like Apple's Mail Privacy Protection (introduced in 2021) have made opens harder to measure accurately — many email platforms now pre-fetch images on behalf of Apple Mail users, inflating open rates. Open rate is still useful for relative comparison (one campaign vs. another), but treat absolute numbers cautiously.

When to use this calculator

  • Measuring the performance of individual email campaigns
  • A/B testing subject lines, sender names, and preheaders
  • Comparing performance across segments, send times, and list types
  • Reporting on email program health
  • Forecasting expected opens for a planned send
  • Setting performance targets for new campaigns

Frequently asked questions

What is a good email open rate?
Open rates vary by industry and list type. Across industries, average open rates typically land between 20–30%, though nonprofit, education, and hobbyist newsletters often see 30–40%+. B2B promotional emails average lower, around 15–25%. Transactional emails (receipts, password resets) often exceed 50% because they're expected. Compare against industry benchmarks and your own historical performance.

How is open rate calculated?
Open Rate = (Unique Opens ÷ Emails Delivered) × 100. If 1,250 out of 5,000 delivered emails were opened, your open rate is 25.00%. Note: use delivered emails (sent minus bounces), not total sent — this is the industry standard.

Why are open rates less reliable now?
Apple's Mail Privacy Protection (launched with iOS 15 in 2021) pre-fetches email images for all Apple Mail users, which triggers open tracking even if the recipient never actually opens the email. This inflates open rates for lists with significant Apple Mail users — often by 10 percentage points or more. Many marketers now rely more heavily on click-through rate, click-to-open rate, and conversion metrics instead.

Should I use unique opens or total opens?
Unique opens — count each person once regardless of how many times they open. Total opens inflates the number and makes comparison across campaigns unreliable. Unique opens are the standard metric reported by virtually all email service providers.

How do I improve my open rate?
The single biggest lever is the subject line — test frequently, keep it relevant, and avoid spammy language. Sender name matters more than most people realize (emails from a recognizable human often outperform generic brand names). Send time, list hygiene (removing inactive subscribers), preheader text, and sender reputation also affect open rates. Most gains come from consistent testing over time.

What's the difference between delivered and sent?
Sent is the total number of emails you attempted to deliver. Delivered is the number that actually reached an inbox — sent minus hard bounces (permanent delivery failures) and soft bounces (temporary failures). Open rate is calculated from delivered, not sent, because you can only open an email that reached your inbox. Most email platforms report both numbers.

Should I track opens, clicks, or both?
Track both, but lean on clicks as the more reliable performance metric — especially post-iOS 15. Clicks require an actual human action and can't be inflated by image pre-fetching. Many email marketers now consider click-through rate and click-to-open rate more meaningful than open rate alone.

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