There are a lot of components to a successful email marketing campaign, and one of those is an effective subject line. In fact, there are various sub-components of that. One is the length. Are longer or shorter subject lines more effective? Is there a sweet spot character count that you should strive for all the time?

If you look at a lot of articles on this subject, you’ll likely find a general consensus that you should keep a subject line’s length to somewhere in the 40 – 50 character range or less.

“The best email subject lines are short, descriptive and provide the reader with a reason to explore your message further,” says MailChimp.

A recently released study from Return Path, however, found no correlation between the length of a subject line and its read rate. In fact, it found that while most subject lines were between 41 and 50 characters, those in the 61 – 70 range had the highest read rate at 17%. They analyzed over 9 million subject lines received by over 2 million subscribers from January 1st through February 28th.

Just because there’s no specific correlation between length and read rate doesn’t mean you can fully ignore how many characters are in your subject line,” the report says. “Different devices have different display capabilities, so it’s important to keep this in mind as you write your subject lines. A typical desktop inbox displays about 60 characters of an email’s subject line, while mobile devices show just 25-30 characters. If your audience is primarily reading your emails on smartphones, place the offer or call to action at the beginning of the subject line where it’s more likely to be seen.”

“Being mindful, too, of how your subject lines may be truncated can also avoid embarrassing brand mistakes, like ‘license’ being truncated to ‘lice,'” it adds. “Shorter subject lines may see higher performance for a mostly mobile audience, too. Look at your existing data for insights like this, or use subject line length as one of your next elements to test.”

Return Path utilized the Pearson’s correlation model to determine the relationship between the number of characters in a subject line, and whether or not that email was opened. On the scale of -1 to 1, with 0 representing no correlation, they found the value to be -.03.

“Read rates happened to be substantially better for both slightly longer and slightly shorter subject lines, but any appearance of correlation is clearly random,” Return Path said in a press release. “Outside of obviously overlong examples, this research suggests that subject line length debate should be put to rest.”

Last year, ShowMeLeads President Madhu Gulati cited research analyzing 260 million emails from 540 campaigns, and finding that subject lines with 6 to 10 words saw a 21% open rate while those with 5 or less words saw an open rate of 16%. Those with 11-15 words saw a 14% open rate.

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