Introduction to the Email Open Rate KPI
The Email Open Rate KPI measures the percentage of recipients who open your email campaign. It’s one of the most fundamental indicators of email marketing performance, showing how effectively your subject lines, sender reputation, and audience targeting encourage subscribers to engage.
What Is Email Open Rate?
Email Open Rate shows how many people opened an email out of all the messages successfully delivered. The formula is:
(Number of Opens ÷ Number of Delivered Emails) × 100
A strong open rate indicates that your subject line is compelling, your timing is effective, and your audience trusts your brand enough to open your messages.
Why This KPI Matters
Email Open Rate provides essential insight into top-of-funnel engagement. It helps businesses understand:
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The effectiveness of subject lines and preview text
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Audience interest and list quality
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Sender reputation and email deliverability
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Optimal timing and frequency of campaigns
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Early indicators of future engagement and conversions
Low open rates may signal poor targeting, unengaging subject lines, or deliverability issues.
How to Use This KPI Effectively
Marketers typically compare open rates by segment, email type, device, and sending time. Pairing this KPI with Click-Through Rate (CTR), Conversion Rate, Bounce Rate, and Unsubscribe Rate provides a complete view of email campaign performance and subscriber engagement.