Email Open Rate Calculator

Practical guide

This calculator helps you calculate an email campaign open rate using delivered messages. It uses two inputs: unique opens and delivered emails. In this tool, unique opens are the number of distinct opens, and delivered emails are the messages that reached inboxes or recipients.

To use it, enter your unique opens in the first field and your delivered emails in the second field. The calculator applies the open rate method shown here: open rate (%) = unique opens ÷ delivered emails × 100. The result is a percentage that expresses how much of the delivered list opened the message.

A simple example is 200 unique opens from 1,000 delivered messages, which gives a 20% open rate. When selecting inputs, make sure the delivered emails value reflects what was actually delivered, since that is the denominator used in the calculation.

Use the result as a campaign-level indicator rather than a full measure of success. A higher open rate can suggest more people opened the email, but it does not by itself show deeper engagement or action after the open.

Keep the limitations in mind when interpreting the result. Privacy features can inflate or obscure open counts, so the displayed open rate may not perfectly match real reader behavior. Opens also do not guarantee engagement, response, or conversion.

For best use, compare open rate alongside other campaign metrics and treat it as one part of email performance review. If the inputs seem unusual, double-check that you selected unique opens and delivered emails correctly before relying on the output.