Open Rate
The percentage of email recipients who opened a given email campaign, used as a primary measure of subject line and sender performance.
Definition
Open rate is an email marketing metric calculated as the number of unique opens divided by the number of emails delivered, expressed as a percentage. It’s one of the most widely tracked metrics in email marketing and is used to gauge how compelling a subject line is and how engaged a list is.
Why it matters
An email that isn’t opened has no chance of driving action. Open rate serves as the first gate – if it’s low, even a perfect email body won’t matter. Tracking open rate over time reveals list health, sender reputation trends, and the effectiveness of different subject line strategies.
Example
If you send a newsletter to 10,000 subscribers and 2,400 open it, your open rate is 24%. Industry averages vary widely – B2B newsletters often see 20–30%, while promotional retail emails may average 15–20%. Note: Apple Mail Privacy Protection (MPP), introduced in 2021, has made open rate tracking less reliable for lists with many Apple Mail users.