Email Open Rate Calculator

Enter opens and delivered emails to find the email open rate.

How it is calculated

The open rate is the share of delivered emails that were opened: rate = opens ÷ delivered × 100. The unopened count is delivered − opens. Use the number of delivered emails (sent minus bounces), not the number sent, and use unique opens, where each recipient counts once however many times they open the message. Both numbers must be whole, delivered at least 1, opens not negative and opens not above delivered; otherwise the tool shows no result. A tracked open is usually a hidden image being loaded, so the rate only counts recipients whose mail app loaded it. It is a relative signal for comparing campaigns, not an exact headcount of readers.

Worked example

A newsletter was sent to 10,000 addresses, 200 bounced, so 9,800 were delivered. Your email platform reports 2,150 unique opens. Divide opens by delivered: 2150 ÷ 9800 = 0.2194. Multiply by 100: 21.94%. The unopened emails are 9800 − 2150 = 7,650. The tool shows an open rate of 21.94%, 7,650 unopened and 9,800 delivered. Had you divided by the 10,000 sent, you would have got 21.50%, a lower and misleading figure.

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Common mistakes

  • Dividing by emails sent instead of emails delivered. Bounces never reached an inbox, so including them understates the rate, here 21.50% instead of 21.94%.
  • Entering total opens, which counts repeat opens by the same person, instead of unique opens. The rate can then look far too high, and once opens exceed delivered the tool shows no result.
  • Comparing rates measured before and after a privacy feature that loads images automatically. Machine-generated opens raise the rate without any extra reading.
  • Entering an average or a percentage in place of a count, such as 2150.5 opens. Both fields are whole email counts and a fraction gives no result.
  • Mixing campaigns or time windows, such as opens collected over a week against a count delivered that day. Both numbers must refer to the same send.

Sources

About this calculator

Email open rate is calculated as unique opens divided by delivered emails (not total sent — bounced emails are excluded), expressed as a percentage, and it’s traditionally been the go-to metric for judging how compelling a subject line and sender name are at getting someone to click into an email.

Email marketers should read open rate with some caution today: since Apple’s Mail Privacy Protection launched in 2021, Apple Mail can pre-fetch images and register an “open” automatically for a large share of recipients regardless of whether a human actually looked at the email, inflating reported open rates industry-wide. Even so, marketers still track it as a rough engagement signal and to A/B test subject lines. This calculator divides opens by delivered emails to give you the open rate along with the number of unopened emails.

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