Open rate is the percentage of delivered emails that were opened by recipients. It’s one of the main metrics in email marketing and outbound sales used to measure the effectiveness of subject lines.

While it doesn’t guarantee the email was read, a strong open rate often indicates a good deliverability rate and strong message relevance.

Open rates can be affected by privacy features (like Apple Mail Privacy Protection), which may inflate results by auto-opening emails. Therefore, they should be used alongside other engagement metrics (like click-through rate or reply rate) for a more accurate performance picture.

Formula:

Open rate = (Unique opens ÷ Delivered emails) × 100

Example:

If you send 1,000 emails and 250 are opened, your open rate is: (250 ÷ 1,000) × 100 = 25%