Email Open Rate Calculator.

Delivered is the usual convention, because a bounced email cannot be opened. Sent is a fair base when your tool cannot tell what was delivered: SendCanyon divides by emails sent for that reason, since a server accepting an email does not prove it arrived. Compare open rates only on the same base, or the difference between the two bases will look like a change in results.

Unique opens count each email once, however many times it was opened. Total opens count every time the tracking image loaded, including re-opens and previews. Open rate uses unique opens. A rate built on total opens can pass 100% and measures repetition rather than how many people opened the email.

It inflates them. Apple says the feature downloads remote content in the background by default, regardless of whether you engage with the email. The tracking image therefore loads for emails nobody read, so Apple Mail users with the setting on can show as opened soon after delivery, and the time of those opens tells you nothing.

Only if your sending tool flags them. Some email platforms mark or filter opens that came from Apple's privacy relays. Enter that flagged count in the optional field and the calculator shows the open rate without those opens. It never applies a flat discount, because no published figure says what share of your own list uses the feature.

There is no verifiable industry average to measure against. Published averages come from each platform's own customers, are often years old, and include opens recorded by privacy features for unread email. Compare your own campaigns on the same base and a similar audience over time, and give clicks and replies more weight than opens.

Usually total opens were entered instead of unique opens, or bounces were counted twice. An open rate can never pass 100% of delivered emails, so the calculator refuses opens above delivered emails and tells you which number to check, instead of printing an impossible rate.

The common causes are open tracking switched off, a plain-text email with no tracking image, recipients whose mail apps block images, or email landing in spam. A zero usually means tracking was not running. A low rate that dropped suddenly on the same list is a reason to check whether your email still reaches the inbox.