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How long should my email subject line length be?

Last updated: September 25, 2023

You spend precious time creating emails that will resonate and drive revenue for your business. But if your subject lines don’t convince audiences to read more, your campaigns could stall out before they even get started. (No pressure!)

The most effective subject lines need to grab the attention of your reader and tell them what they can expect to gain from the message — all in the half-second the reader spends scanning their inbox.

So your subject lines need to be short enough to get the point across, but long enough to provide necessary context.

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That can be a hard balance to strike: How long is too long? How much do opens and clicks really fall if your email subject line goes over 30 or 40 characters? And ultimately, what is the best email subject line length?

To learn more, we analyzed more than 1.6 billion emails sent through our platform during Q3 2022. But as with any research, correlation doesn’t equal causation. And what resonates with the average user may not move your audience. So we recommend testing your subject line length and content with your audience and paying special attention to your performance on non-Apple devices like Gmail and Outlook, since their open and click rates are not impacted by MPP protections.

Here’s what we found:

What is the ideal length for my email subject line?

When it comes to subject lines, shorter is better:

The average open rate is 29.9% for subject lines with 20 characters or less. From there, performance drops significantly: The average open rate dropped by more than one-third to 17.3% for subject lines between 20-124 characters.

Interestingly, performance recovers a bit once email subject lines exceed 174 characters, although not the level of ultra-short subject lines: Open rates rise to 23.2% when the subject line is between 174-224 characters and 22.7% for subject lines with 225+ characters.

That said, given the steep penalty for lengthy email subject lines, we recommend using super-long subject lines only when your offer is extremely compelling or when you’re presenting truly ground-breaking research (and when in doubt, err on the side of going too short).

4 subject line best practices to use:

Optimizing for length is only the first step to creating a successful subject line, though. To get the best performance from each send, you need to follow general subject line best practices. That includes:

1. Keep the most important information in the first 30 characters of your subject line

What good is a catchy subject line if your audience’s mobile browser cuts it off halfway through? Mobile inboxes display only the first 33-43 characters of a subject line, so get to the point in the first 30 characters.

2. Use the preheader text to enhance your message

Struggling to cut your subject line down? Use the preheader text to give readers more context — and elicit more interest in your content.

3. Experiment with different email subject lines and lengths

Running A/B tests on your subject lines allows you to test multiple options at once, then change your campaigns to meet audience preferences in real time. (On Omeda, you can run up to five tests in one campaign.)

4. Only send emails to opt-ins

If you’re targeting audiences that aren’t interested in your content, they won’t open your emails, regardless of the subject line. Instead, only send to people who have actively opted in to receive emails from you — and run re-engagement campaigns to reconnect with passively engaged users. This way, your open rates will beat our averages every time.

Want to build an email engine that grows your business? Omeda’s end-to-end email marketing solution empowers you to build, automate and evaluate mass email marketing campaigns, then connect your data back to an integrated marketing database engine. Reach out to us at sales@omeda.com to schedule a demo and get started today!

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