Open rate measures the percentage of email recipients who opened a given message, calculated as opens divided by emails delivered, though the number has become less reliable in recent years due to how inbox providers handle image loading.
The Formula
Open Rate = (Unique Opens ÷ Emails Delivered) × 100
How to calculate open rate this way ties the result to unique recipients rather than total open events, since one subscriber opening an email three times shouldn’t count as three separate opens for measuring reach.
Why the Number Doesn't Mean What It Used to Mean
Open rate tracking relies on a tiny tracking pixel loading when an email is viewed. Apple’s Mail Privacy Protection changed that mechanism significantly, pre-loading images, including tracking pixels, the moment an email lands rather than when a recipient actually opens it:
- Roughly 64 percent of B2C email subscribers use an MPP-capable version of Apple Mail, meaning the majority of most ecommerce lists now generate inflated open data automatically.
- This affects reported opens uniformly across a list, which means comparing open rate over time is still useful for spotting trends, but comparing the raw number against an old, pre-2021 benchmark is comparing two different measurement realities.
Open Rate Benchmark by Send Type, Not Just Overall
Open rate benchmark figures vary far more by send type than most flat industry averages suggest. Klaviyo’s 2026 data across more than 183,000 ecommerce brands found:
- Campaign open rate: averaging around 31 percent overall, with a range of roughly 28 to 33 percent depending on sub-industry, and top performers exceeding 45 percent.
- Welcome flow open rate: 40 to 60 percent, considerably higher than campaigns since the recipient just signed up and expects the message.
- Clothing and accessories specifically: averaging around 33 percent, with 33 to 45 percent considered above average and anything above 45 percent landing in the top 10 percent of senders.
Comparing a welcome flow’s open rate against a broadcast campaign’s is comparing two fundamentally different intent states, not a fair apples-to-apples benchmark.
Open Rate vs Click Rate
Open rate vs click rate is worth distinguishing clearly given the MPP distortion above:
- Open rate measures whether the subject line got attention, though it’s now partly an artifact of automatic image pre-loading rather than pure human behavior.
- Click rate requires genuine recipient action, a real click, which MPP doesn’t fake or inflate.
This is why click rate and conversion rate have become more trustworthy performance signals than open rate alone for judging whether a campaign actually worked.
Related terms:
A quick working answer to what is open rate worth remembering: a useful trend indicator, not a precise measure of genuine human attention anymore, given how MPP has changed what actually gets counted as an open. For a full breakdown of every metric worth tracking and how Adflipr’s dashboard reports each one, see our Email Marketing Analytics guide.
