What is the Best Email Subject Line Length?

Which are better; shorter subject lines or longer subject lines?

The email subject line length is a highly debatable topic for two simple reasons.

  1. First of all define short and long in this context. There is no absolute correct answer.
  2. Secondly, there is some tension between ‘short and to the point’ versus ‘giving as much information as possible’.
Email Subject Line Length

As an email marketer the subject line of your email is the opportunity to get a reader to open up your message. Fail to convince your reader to open it and your message was send in vain.

As could be expected research is divided. People are still looking for the golden rule but it seems there is none.

There are however some things you should consider.

In my experience, shorter subjects lines usually have a higher open rate and could also have an higher click through ratio (CTR).

Now I know there is research out there that suggest longer subject lines might be better, so my statement might sound somewhat counter intuitive.

Let me explain why I think shorter subject lines are better.


Technical limitations

First of all there are some technical recommendations about text messages on the internet. RFC 2822 gives the following recommendations.

Section 2.1.1 – Line Length Limits

There are two limits that this standard places on the number of characters in a line. Each line of characters MUST be no more than 998 characters, and SHOULD be no more than 78 characters, excluding the CRLF.

The takeaway is that your subject line should not be longer than 78 characters. This is only a recommendation though. Section 2.2.3. talks about Long Header Fields and discusses the option to ‘fold’ long lines.


Research on the subject

In 2012 Mailchimp analyzed 12 billion emails that were send through their system and analyzed how the subject line length had an effect on engagement.

If you only read the top half of that article you might think that their conclusion was that there is no significant correlation. In other words it would make no difference.

However, if you read the second half of that article you’ll discover that there are more factors at play here. There are more things to consider. The bottom line is that you will have to figure out and test this for your audience.

In one of their follow up articles they give us some good advise. The conclusion is to not sell what’s inside but to tell what’s inside.


What do readers think about the lenght of subject lines?

Put yourself in the shoes of your reader for a second. Would you open and read your own emails?

What is working against you is the ability of your readers to filter out information. If you understand how that process works you can craft your email subjects to go right through their filters.

The very first thing that you do when you open your mailbox is probably to skim over all the emails and briefly glance at the senders and subject lines.

There is an important difference between reading and skimming. When skimming you’re basically looking for some keywords that tell you what the message is all about. You’re not actually reading the entire subject at that moment.

Go ahead and try this for yourself. How long does it take you to look at your inbox before you start opening emails? If your answer is something like ‘briefly’ or ‘short’ you are skimming, not reading.

Am I right?

I know I am.


The reason you and I do this is because we want to filter out the bulk of those emails. We’re all being flooded with information each and every day and We’re also all in a hurry.

We don’t want to read through pages of emails to find out if we really wanted to read it in the first place.

We want to get a quick grasp of the information in those emails. Skimming is hard wired into our brains and it serves as a first rough filter to get rid of 95% of the information in front of you.

Shorter subject lines are faster to read (or skim) and usually easier to understand. They have to be to the point. If they aren’t they’ll be discarded right away.

Also consider that more people are now reading email on their mobile phones which have smaller screens. A shorter subject line is more user friendly in those cases. Even if they zoom in it will still be easy to oversee the entire wrapped subject line.

FACT: Did you know that as of 2014 more people read their email on a mobile device then they do on their laptop or computer?

Not catering for mobile users is the same as leaving money on the table.


But there is a pitfall here.


The subject line must cover the content of your email. If you trick your readers by using a subject line that is not directly related to your email content you will annoy them.
If they don’t unsubscribe immediately, they probably ignore or trash your next emails.

Don’t overdo the shortening of your subject line. Make sure it explains what your email is about. Very short subject lines (5 words or less) are unconsciously already being categorized as probable spam. How can 5 words cover the content in your email, right?

Longer subject lines usually describe the content of the email better, leading to a more satisfied reader (he got what he expected) which in turn results in higher CTRs.
However, having to make the effort to  read and grasp the content of a long subject line is a turn off.

If you are skimming you’re not likely to interrupt that process for some reading. You might read it afterwards if you didn’t delete that email already. That is providing you didn’t forget it and aren’t reading other emails or viewing a website.

Getting your message across fast and clear is going to work in your favor.

It is an art to create a short and catchy subject line that accurately covers the content of your email. It also has to trigger a (preferably strong) emotion to snap your reader out of the ‘zombie state’. I explain this in more detail in my free ebook Smarter Affiliate Success Secrets that you get for free if you sign up for my list. If you can do all that you have a winner on your hand.

As always you must measure your success rate. I recommend you even start doing split testing. Send the exact same email with two different (but relevant) email subjects to equal parts of your list. May I suggest a long and short subject line? See which one gets the best opening rate.

Test, test and then test some more. Rinse and repeat.



  • There is no one size fits all solution. What works best for your audience is something you will have to test.
  • I recommend you keep subjects short and to the point but make sure they cover the load.
  • Try to trigger an emotion in your subject line, this helps the reader to remember your email so there’s a higher chance that it will be opened.
  • There are more tricks that you can use to get your emails opened, like to two awesome tips from my other post.


So there you have it.

In one my next posts I’ll give you a few solid tips to construct a powerful subject lines.

Good luck with your emails!



4 thoughts to “What is the Best Email Subject Line Length?”

  1. Hi Remco.

    An intelligent and research led article. Kudos.

    However, I think a lot of marketers put too much effort into this area. Of course, a solid email subject line is important, but I tell you what is even MORE important:

    The line above it.

    Yep, the line above it, that tells the subscriber who the email is from.

    I am more than likely to open and read an email from a person who I like, admire and trust, regardless of the subject line.

    So here is what I say – forget about spending time putting energy and effort into subject lines, and start making more effort to be liked and trusted by people – this is something I am taking into 2015 and beyond.

    Thanks Remco.

Leave a Reply

Your email address will not be published. Required fields are marked *