Email subject lines are truncated at different lengths depending on the device and email client. Getting cut off mid-word is a credibility killer. Here is exactly how many characters you have — and the optimal length for maximum open rates.
Subject Line Display Limits by Email Client
| Email Client / Device | Characters Displayed |
|---|---|
| Gmail (desktop) | ~77 characters |
| Gmail (mobile) | ~40 characters |
| Outlook (desktop) | ~73 characters |
| Apple Mail (desktop) | ~60–70 characters |
| iPhone (mail app) | ~35–40 characters |
| Android (Gmail app) | ~40 characters |
| Apple Watch | ~30 characters |
Optimal Subject Line Length for Open Rates
Research on millions of email campaigns consistently points to two sweet spots:
- Under 30 characters: Very short, punchy subject lines perform well for engaged lists. Example: “Quick question” or “Re: your message”
- 40–50 characters: The general sweet spot that balances enough context with mobile compatibility
- 50–70 characters: Acceptable for desktop-heavy audiences but risky on mobile
- Over 70 characters: Almost always truncated; avoid unless you are deliberately front-loading the hook
Front-Loading Your Subject Line
The most important principle for email subject lines is front-loading: putting the most important words first. Since truncation always happens at the end, your critical information — the offer, the question, the news — must be in the first 30–40 characters.
Bad: “We have some exciting news about our new product launch that we think you will love” (truncated before the news)
Better: “New: [Product] launches today — here is why it matters” (key info in first 30 chars)
Subject Line Formulas That Work
- Question: “Are you making this mistake?” (36 chars)
- Number: “5 things to do before Friday” (30 chars)
- How-to: “How to write a cover letter in 20 minutes” (43 chars)
- Urgency: “Last chance: ends at midnight” (30 chars)
- Personalisation: “[Name], your report is ready” (varies)