Email Subject Line Length Calculator
Analyze Email Subject Line Length
Subject Line
0 characters
Preheader Text (Optional)
0 characters
Subject Length: Optimal subject lines are 20-50 characters. Mobile devices show 35-40 chars, desktop shows 60-70. Keep important words at the beginning!
Testing this tool with an AI agent
- Open this page in a browser. Email Subject Line Length Calculator is the form at the top of the page.
- Fill every field with sample values. Use made-up data, never real customer data.
- Press the main button and wait for the result to show on the page.
- No login, API key or install is needed.
What it does
- Length analysis
- Preview simulation
- Device testing
- Truncation warning
- Character counting
When to use it
- Subject optimization
- Preview testing
- Mobile optimization
- Character limits
About Email Subject Line Length Calculator
The Email Subject Line Length Calculator shows how your subject line displays across different devices, clients, and preview scenarios.
Frequently asked questions
How does Email Subject Line Length Calculator work?
Fill in the form at the top of this page and run it. The result shows on the same page. No account or install needed.
Is Email Subject Line Length Calculator free?
Yes. It is free and needs no signup. Use it as often as you like.
How much should I trust the result?
Use it as a quick check. It follows common email marketing calculators rules, so check anything important again before you change live settings.
Can I use it for work?
Yes. You can use it for personal and work tasks.
Should I paste private data into it?
No. Like any online tool, never paste passwords, API keys or private customer data.