Determining the Ideal Length for Your Email Subject Lines

Being a marketer, you pour in your best efforts to prepare a great copy and build a persuasive email. But if your subject line is mundane and does not push the receivers to open your email and read it, your campaign might fail terribly.

The time is changing, and now emails are being increasingly opened using mobile devices, which displays fewer characters of subject lines. Now you must be thinking if you should start keeping your subject lines short enough to serve your on-the-go email subscribers.

What is the secret ingredient to finding the best length for your email subject lines?

Since every email subscriber list is different, the ideal length of your subject lines relies on numerous elements. However, you can still get a bit of insight into perfect subject line lengths for your niche or industry.

In this blog, we will resolve all your worries and help you determine the perfect lengths for your subject lines.

Factors to Consider While Determining Your Email Subject Line Length

There is no definite subject line length that we can say is the best. As we mentioned earlier, your email subject line’s ideal length relies on several factors.

  1. Devices and Readers Your Emails Are Being Opened on

In the past couple of years, we saw a massive shift from desktops to mobiles, and today the majority of the emails are being opened on mobile devices.

However, it is crucial to remember that different subscribers use different web browsers and email readers. Thus, complicating the whole process of finding a definite subject line length for your emails.

So, when identifying the perfect subject line length for your emails, make sure you consider the devices that your subscribers are using to access your emails using your data. Is the majority of your email readers using their mobiles to open your emails or sticking with desktops?

Most of the email tracking platforms allow users to obtain this information from their account itself. Be sure to use a tracking tool that lets you do this as it will help optimize your email subject line length.

For instance, let’s say, as per the data, you found that most of your emails are being opened on Gmail and iPhone, now you can optimize your subject line length according to them.

  1. Review the Performance of Your Past Email Subject Lines

It is always a good idea to take a quick peek into your past to improvise your future performance. Therefore, analyze which subject lines of your past emails have accumulated the highest open rates.

Now, there can be a lot of reasons behind these high open rates – it can be your offer, time of the day when the email was sent, your copy, or the emotion portrayed in your subject line.

But still, it’s always good to have a look at past performances and check if you can see any emerging trends from your email open rates and your subject line length.

How Many Characters Are Ideal for Your Subject Line?

As you sit down to create your email subject line, keep in mind when and how your audience is opening or reading your emails.

For instance, if most of the reads are coming from iPhones, it is best to use shorter subject lines to cast the most impact. Moreover, try keeping your call to action or offer at the starting of your subject line as then there will be more chances of it getting noticed by the receivers. You can also add more context to your subject lines using the preheader text, which is displayed in the preview pane just below the email subject line.

How to Test Your Email Subject Lines?

One of the easiest elements to test in your email campaigns is your subject line. By carrying out tests, you will be able to see how your subject line will appear across different devices. It also lets you compare the performances of its shorter and longer versions.

  • Sending out test emails will help you review how your subject line performs on different devices. It will help make sure your email subject line reads fine everywhere.
  • Conduct an A/B test on two different subject line lengths. Some email providers let you test two different subject lines to see their performance. It would be best if you text a short and a long version to find out the optimal one.
Leveraging Best Practices for Email Subject Lines

Indeed determining the perfect subject line length is crucial in email marketing, but bear in mind that it is not all about length. To be successful, you will have to leverage the best practices for subject lines.

  • Always use different subject lines – If you keep repeating your subject lines, using the same old ones will bore the audience. Using fresh new original subject lines inspires the audience to engage with your email and see what you are the latest offer you have brought to them.
  • Personalization is the key – Audiences love it when brands connect with them on a personal level, and using personalization right in the subject line will do wonders for you. Maybe you can add the recipient’s name in the subject line, or there are plenty of personalization options available; all you need to do is go through the subscriber data. You can gather this data using your sign up forms or other external sources.
  • Conduct A/B test – Unless you explore and try out different options, you will never know which one was the best. So, do an A/B test on your subject lines to discover the optimal one.
Finding the Perfect Length for Your Email Subject Lines

As compared to other marketing channels, email marketing continues to offer the best ROI even today. However, it all begins with that one short, crisp, and an intricately crafted subject line that persuades and convinces the receiver to read it.

5 Best Practices for Email Subject Lines

While the subject line length still matters even today, the way you are utilizing the characters allowed in one line has become crucial. And with the increasing use of mobile devices to access emails, this fact is now more critical than ever as typically mobile screens have a shortened display showing just 30-40 characters.

  1. Shorter Subject Lines

While several research studies show that 40 characters are an ideal length for an email subject line, on the other hand, marketing experts recommend to keep it even shorter. And there are two primary reasons behind it.

The first being, emails that have shorter subject lines have more chances of being delivered, and the second is that conciseness builds an air of mystery.

Let’s understand this with an example. The subject line – “Will you be able to meet me at 10 today?” (40 characters) does not really have the same impact as “Meeting at 10?” (14 characters).

  1. Emojis

Even though there has been quite a buzz around emojis always, the truth is that they are here to stay for a very long time. Using them wisely in your subject lines can help your emails stand out in an inbox with apparently piled up text lines.

Plus, there are several other benefits associated with the use of emojis. Most businesses prefer not to use them, and therefore, this might grab a higher response rate for emails that are using them.

Moreover, these emojis also build a powerful emotional narrative, which is ideal for conveying your message in the shorter lines of text across mobile devices.

  1. Capitalization

The chances are that you are not considering the way you capitalize your email subject lines, but you should give it a thought. Typically, there are four capitalization styles:

  • Writing the perfect subject line for your email (sentence case)
  • writing the perfect subject line for your email (lowercase)
  • Writing the Perfect Subject Line for Your Email (title case)

According to a study, 0% of marketing professionals used uppercase capitalization. The majority of them used sentence case capitalization, some used title case capitalization, and a tiny percentage used lowercase capitalization for their email subject lines.

Even after being used very less often, several renowned marketing experts attribute lowercase capitalization with higher open rates because it adds a more personal and casual feel to the email.

  1. Personalization

Adding a personal touch to your email subject lines by incorporating the name of the receiver in it is a conventional tactic to increase open rates. However, based on your email content or offer, you can use different types of personalization with the help of your data.

For example, if you work for a travel company, based on past user behavior, you can send a personalized email with a subject line – “Still wondering about Paris?” Now, this is a strong subject line because it is short and to the point, it raises a question, and it’s related to the recent activities of the recipient. Try doing the same with your emails and experience the magic.

  1. Avoid Spam Filters

Every single email that you send, which lands up in the recipient’s spam folder, is a missed chance for conversion or any action that helps us build a connection with the receiver. Therefore, do proper research and omit all the words from your subject lines that trigger spam.

However, apart from word choice, several actions might lead you straight into the spam folder, for instance, using all capital letters. However, make sure you don’t use any words and phrases to avoid spam filters.


At last, the ideal email subject line length will heavily depend on your purpose, industry, audience, device, email reader, and so on. It varies from company to company, and there is no one-size-fits-all length. Therefore, the best way is to test out different subject lines to see which one works best for you.

By leveraging your previously collected data and running tests on your subject lines, you will be able to determine the optimal length for your email that will push the recipients to open, engage, and respond to your email effectively.