How long should your email subject line be?

Email subject line length

The ideal email subject line length is 30 to 50 characters. This range ensures your full message displays on most devices and email clients without getting cut off.

Mobile screens show the least, typically 33 to 43 characters. Desktop inboxes like Gmail can display up to 70 characters, while Outlook shows around 50. Since most emails are now opened on phones first, writing for the smallest screen protects your message everywhere.

Why subject line length matters

Your subject line is the first thing subscribers see. If it gets truncated mid-thought, you lose the hook that convinces someone to open.

Shorter subject lines also tend to perform better. Open rates drop as word count increases, with the steepest decline happening after you pass 50 characters. The sweet spot for most brands falls between 4 and 7 words.

Beyond opens, length affects deliverability. Overly long subject lines packed with promotional language can trigger spam filters, while keeping things concise signals legitimacy to inbox providers.

Character limits by device and email client

Different platforms display different amounts of your subject line:

• iPhone (Apple Mail): 48 characters
• iPhone (Gmail app): 37 characters
• Android (Gmail app): 33 characters
• iPad (Apple Mail): 39 characters
• Gmail (desktop): Up to 70 characters
• Outlook (desktop): Around 50 characters

The safest approach is to front-load your most important information in the first 30 characters. That way, even if the rest gets cut, your core message lands.

How to write effective short subject lines

Getting your point across in under 50 characters takes practice. Here's how to make every word count.

Lead with the benefit. "20% off ends tonight" beats "Don't miss our special limited-time discount offer." The first version is 21 characters; the second is 52 and says less.

Cut filler words. Words like "just," "really," and "actually" rarely add meaning. Remove them and your subject line tightens immediately.

Use your preheader text. The email preheader gives you extra real estate to expand on your subject line. Think of them as a team: the subject line hooks, the preheader explains.

Try a question. Questions create curiosity in fewer words. "Ready for summer?" works harder than "Get ready for our summer collection launch."

When longer subject lines work

Short isn't always better. Context matters.

Transactional emails often benefit from specificity. "Your order #4521 has shipped" tells the recipient exactly what to expect, and cutting that down would create confusion, not clarity.

Personalized subject lines that include a product name or location may run longer, and that's fine. "Sarah, your favorite moisturizer is back in stock" is 47 characters but earns the length through relevance.

The key is testing. Run A/B tests on your subject lines to see what resonates with your specific audience. What works for one list may flop for another.

Subject line length for different email types

1. Welcome emails: Keep them warm and brief. "Welcome to [Brand]" or "You're in!" works well.
2. Promotional emails: Front-load the offer. "30% off today only" outperforms vague teasers.
3. Abandoned cart emails: Mention the product if space allows. "Still thinking about those sneakers?" creates recognition.
4. Newsletters: Highlight the most compelling story. "3 ways to boost your open rates" gives readers a reason to click.
5. Re-engagement emails: Be direct. "We miss you" or "Still interested?" cuts through inbox noise.

FAQs

What's the best email subject line length for mobile?
Aim for 30 to 40 characters. The Gmail app on Android shows only 33 characters, making it the most restrictive common email client.

Do emojis count toward character limits?
Yes. Most emojis count as 2 characters due to how they're encoded, so use them sparingly and test how they render across devices.

Should I use all caps in subject lines?
Occasionally, for emphasis. "LAST CHANCE" can create urgency, but overuse looks spammy and may hurt deliverability.

How do I know what length works for my audience?
Check your email platform's reports to see which devices your subscribers use most, then A/B test different lengths to find your optimal range.

Want to test what works for your audience? Start your free ActiveCampaign trial and run your first subject line A/B test today.