# Subject line tester

Source: https://joinbreaker.ai/subject-line-tester

**Test your email subject line against 100+ variables.** A free interactive tool (use it on the page above): enter a subject line and it returns a score out of 100 with a quick assessment, so you can rework the line and rescore until it's ready to send.

Related: the [newsletter ROI calculator](https://joinbreaker.ai/roi-calculator.md), and Breaker's blog guides on [email subject line best practices](https://joinbreaker.ai/blog-posts/email-subject-line-best-practices-3cd9e.md) and [funny email subject lines](https://joinbreaker.ai/blog-posts/funny-email-subjects.md).

## Breaker pricing, for reference

- **Starter**: $200 per month. 100 new engaged subscribers per month, up to 50,000 sends, 7-day trial.
- **Custom**: $1,750 per month. 1,000 new engaged subscribers and 250,000 sends per month.
- All plans include precision audience targeting, unlimited email validations, the newsletter builder, unlimited users, performance analytics, signup forms, and white-glove support.