Complete and up-to-date character limits for every Email Subject Line element. Use the free character counter below to check your content before posting.
Quick Answer
Email subject lines should be 30 to 50 characters for maximum visibility across all email clients. Mobile shows only 30 to 38 characters so put your most important words first.
The optimal email subject line is 6-10 words or 30-50 characters. This ensures the full subject displays on mobile devices without truncation. Mobile email opens account for over 60% of all email opens, so mobile display is the primary design constraint.
Subject lines over 60 characters get truncated on most mobile email clients. The truncated portion is invisible — the reader cannot even guess what it said. If your key message is in the second half of a long subject line, it will never be read.
Gmail displays about 70 characters on desktop and 35-40 on mobile. Outlook shows about 73 on desktop and varies on mobile. Apple Mail shows 55-65 on desktop. The safe zone across all clients is under 50 characters.
Subject Line Formulas That Work
Numbers outperform words: "5 changes to Q3 plan" beats "Updates on the quarterly plan." Specificity beats vagueness in every A/B test.
For cold emails, shorter is better. "Quick question" has an open rate above 50% (Yesware data). Single-word subjects like "Intro" or "Idea" also perform well because they feel personal rather than promotional.
Personalization increases open rates by 22% on average. Including the recipient\'s name or company in the subject line signals relevance. "[Name], your trial expires Friday" outperforms "Your trial is expiring soon."
Urgency works but must be genuine. "Last chance: 50% off ends tonight" drives opens when the deadline is real. Using false urgency trains your audience to ignore future subject lines.
Subject Lines by Email Type
Newsletter: be specific about content. "3 tools I used to double my traffic this month" outperforms "This week\'s newsletter." The subject should give a reason to open, not just announce the email\'s existence.
Transactional: clarity over creativity. "Your order #4523 has shipped" is perfect. Do not try to be clever with transactional emails. People want information, not entertainment.
Cold outreach: keep it under 5 words. Reference something specific about the recipient\'s work. "Loved your talk at [Conference]" gets opened. "Exciting partnership opportunity" gets deleted.
Internal/work emails: front-load the action needed. "[Action Needed] Review budget by Friday" is better than "Budget review request for the upcoming quarterly planning cycle." The first tells you what to do. The second makes you read to figure it out.