Hey there,

Let’s play a quick game:

Which subject line do you think would perform better?

  • A) Tips to boost your email opens
  • B) 7 tips to boost your email opens
  • C) 7 tips to boost your email opens by 38%

If you guessed C, you’re right on the money 🎉

According to Zippia, adding numbers to your subject lines can increase open rates by up to 57%.

Why do numbers work so well?

  • They stand out in a crowded inbox
  • They set clear expectations for the content
  • They appeal to our love for lists and easy-to-digest information

But there’s a catch…

Specific numbers (like 57% or 12 minutes) tend to perform better than round numbers (like 50% or 10 minutes).

Why? Because they feel more authentic and data-driven. They suggest you have precise insights to share.

To make your subject line even more enticing, you can combine numbers with power words, like “new”, “magic”, or “special”.

Some examples to get you started:

  • 4 weird tricks that boosted our email opens by 37%
  • The 13-word subject line that got us 829 new subscribers
  • How we increased click-rates by 22% with one simple change

Need more inspiration? Check out our email subject line generator and receive AI-powered suggestions (for free).

Have you tried using numbers in your subject lines? How did it work for you? Hit reply and let me know. I’d love to hear about your experience :)

Happy sending, Laura