How Long Should An Email Subject Line Be? Best Practices Explained

How Long Should An Email Subject Line Be

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How Long Should An Email Subject Line Be?

How Long Should An Email Subject Line Be

Published by Today Testing Team

Last Updated on May 18, 2022

As a marketer, you already know details matter. And when it comes to email marketing, one of those details is the subject line — not just the content, but the length.

How long should an email subject line be?

The question is more important than you might think.

Your subject line is your first (and sometimes only) chance to make a good impression and convince your subscribers to open your email. So it’s important to get it right!

Most users spend seconds reviewing email subject fields to filter out unneeded or irrelevant communications. Even if the entire body of the email contains relevant and beneficial information for them, if the subject field does not immediately catch their attention, they will go on to the next item in their inboxes. The goal of email subject lines is to get people’s attention, and the length of your subject line plays a big role in this.

The answer to the ideal subject line length, unfortunately, is not a one-size-fits-all thing. It depends on a number of factors, including the type of email you’re sending (e.g. a confirmation email for someone signing up for your list will be different than an email pushing a sale) and your audience.

Let’s get into the basics of what makes a good subject line length. 

Table of Contents

Think Mobile First

If an email subject line is too lengthy, it won’t fully display, especially on mobile screens. With a huge percentage of email openings occurring on smartphones, consider using subject lines less than 50 characters to ensure that it displays properly.

Furthermore, put the most relevant information in the first 30 characters to optimize it for mobile users. It prevents the important info in the subject line from being chopped off.

Tease What's Inside Of The Email

You want the recipient to actually open your email, so the subject line needs to really create intrigue and make what’s inside feel special. 

For example, the subject line could go like ‘the wait is over, here’s your new guide!’. 

The point is you want the reader to feel like they’re missing out on something important if they don’t open your email.

The average person receives dozens of emails per day, which means they have to make some decisions quickly about what’s worth their time and what can be sent straight to the trash. 

Use Terminology That Is Straightforward and Concise

Remember that people scan their inboxes, so make your subject line clear and concise. It’s typically far preferable to be brief than to use technical, jargon-y language that fills up a lot of space.

A good subject line should be specific and informative, so that the recipient knows what the email is about at a glance. 

It should also be concise, so that it doesn’t take up too much of the recipient’s time. 

By taking the time to craft effective subject lines, you can help ensure that your emails are read and acted upon in a timely manner.

Make Others Feel Special and Distinct

The psychology of exclusivity is quite powerful. When consumers feel like they’re getting something special that no one else is getting, it drives them to open your email. Not only that, it fosters loyalty. 

You can do this by saying something like, “John, Here’s Your Exclusive Offer!” in your subject line.

Use The Preheader Wisely

The preheader is the extra text that appears next to or below the subject line in an inbox. Preheaders complement the subject line and may provide that extra bit of information that you might not be able to fit into the subject line. It’s a great way to maximize the info you’re able to deliver while maintaining an ideal subject line length.

Use A/B Testing to Find the Right Subject Line Length

While these recommendations and best practices are excellent beginning points, what works for one business may not work for another. It is more about determining what works the best for your particular audience.

How can you find out which subject line length works best for your audience? 

The answer is split testing. 

Split testing involves sending out two (or more) versions of your email with different subject lines, and then measuring which one performs better. 

For example, you could send out one email with a short subject line and another with a longer subject line, and see which one gets more opens. 

Or you could test different variations of your subject line to see which one gets the most clicks. 

The best email marketing platforms — like Constant Contact, Aweber, and GetResponse — make split testing a breeze.


By split testing different options, you can find the ideal length for your audience, and ensure that your emails always have a winning subject line.

Use Emojis In A Subject Line to Convey Feelings

In recent years, emojis have become an increasingly popular way to communicate online. And while they were originally designed for use in personal messages, emojis can also be a great way to convey information in a subject line. 

A well-chosen emoji can add personality and visual interest to an otherwise ordinary subject line, making it more likely to stand out in a crowded inbox. 

In addition, emojis can help to make a subject line more concise by using a simple symbol to get across an idea or feeling, which can be especially helpful when space is limited. When used judiciously, emojis can be a powerful tool for making your subject lines more engaging and effective.

Final Thoughts on Email Subject Line Length

Email subject lines are often one of the most challenging parts of writing an email. You want to make sure that your subject line is long enough to convey the message of your email, but you don’t want it to be so long that it gets cut off in people’s inboxes. 

So what is the ideal subject line length? 

The answer is that shorter is usually better, but also, it just depends.

The key is to experiment and find what works best for you and your audience.