Open Rate
Open rate measures recorded unique opens as a share of delivered email. Tracking pixels, image blocking, and privacy features limit what it says about readers.
Open rate is the percentage of delivered emails with a recorded unique open. Email platforms commonly record opens when a tracking image loads. That event does not establish that a person read the message.
Calculate it
Divide recorded unique opens by delivered emails, then multiply by 100. In an example with 10000 emails sent, 200 bounces, and 2450 recorded unique opens, the denominator is 9800 delivered emails and the open rate is 25 percent. Count a recipient once for that message, even if its image loads repeatedly.
Read the number with its limits
Image blocking can hide a real read. Privacy services can load an image without a read. Apple's Mail Privacy Protection documentation explains its background loading behavior.
When comparing sends, keep the reporting window, audience definition, and treatment of automated opens consistent. A changed mix of email clients can change the result without a corresponding change in reader interest.
Use opens alongside clicks, replies, and the action the email was meant to support. Clicks can also include automated activity. An open rate alone cannot establish inbox placement or show that a subject line caused a change in sales.