Balancing your email subject line length and coming up with something catchy can be frustrating. Much like writing a tweet, one of the challenges is formulating an enticing phrase with a limited number of characters.

But how long can a subject line be?

Length does matter

From a technical perspective, RFC 2822 (the Internet Message Format) states that the maximum number of characters in a subject line is 998. However, a lot of email clients will impose a 255 character limit.

However, most email clients will only display a certain number of characters before hiding the rest of the message.

We’ve also found that this display limit varies wildly across email platforms.

In their default settings, platforms such as the iPhone displays as few as 41 characters. On a 1024 x 768 screen, Outlook 2010 displays 54 characters in a preview pane, whereas free online portals such as a Gmail, Hotmail and Yahoo range between 46-70 characters.

How length influences engagement

A report by MailerMailer found a correlation between subject line length and open and click through rates. Given the limited number of characters displayed across various devices, it was no surprise that shorter subject lines worked best.

Between four-15 characters saw an open rate of 15.2 per cent and a click rate of 3.1 per cent. 16-27 characters garnered an 11.6 per cent open rate and a 3.8 per cent click rate.

Subject lines with 28-39 characters attracted an open rate of 12.2 per cent and a click rate of 4.0 per cent, while those with over 50 characters typically gained an open rate of 10.4 per cent and a click rate of 1.8 per cent

Middle ground

According to MailerMailer’s report, the ideal subject line length is between 28-39 characters – providing the best overall engagement rate.

Also, when drafting your next subject line, keep in consideration what character restrictions you might run into, especially if you are communicating to a mobile heavy audience, where the average subject line display space is shorter than desktop variants.

ABOUT THE AUTHOR
Wei Tan has over 8 years digital marketing experience and is currently Co-founder of email marketing agency The Orchard. Wei has a passion for email marketing and works closely with some of Australia’s best known brands in developing tailored email marketing programs focused on delivering solutions based on three core principles: Growth, Conversion & Retention.

The Orchard provides email marketing services, including creative, strategic and campaign management.

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