How long should a subject line be?

Most of your subscribers are reading email on their phones. That one fact should shape every subject line you write.

The practical sweet spot is 30 to 50 characters. That range fits comfortably on most mobile screens without getting cut off mid-sentence. Go much longer and you risk the subject line truncating right before the most important word. Go too short and you may not give readers enough to decide whether to open.

Here's a rough breakdown by screen type:

• Mobile (most common): roughly 30 to 40 characters visible before truncation
• Desktop webmail (Gmail, Outlook): typically 60 to 70 characters
• Apple Watch and notification previews: as few as 15 to 20 characters

A subject line like "Your order shipped" (19 characters) works everywhere. "Here's a quick update on the status of your recent purchase with us" (65 characters) gets mangled on mobile. The message is the same. The result is very different.

Front-load your most important words. Don't bury the point after a preamble. "Last chance: sale ends tonight" reads better than "We wanted to let you know the sale ends tonight." Both say the same thing. One earns the tap.

And worth Worth noting: character count and display limits vary by client, so there's no universal magic number. The 30 to 50 range just gives you the best odds across the widest range of devices. If you want to test where your subject lines actually cut off across the major clients, our free subject line tester shows you exactly that.