Email subject line formulas are something I wish I’d paid attention to much earlier in my blogging journey. For the first year, I’d spend an hour writing a genuinely useful email and then dash off a subject line….
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Email subject line formulas are something I wish I’d paid attention to much earlier in my blogging journey. For the first year, I’d spend an hour writing a genuinely useful email and then dash off a subject line in 30 seconds before hitting send. My open rates showed it.
Your subject line is the only part of your email that everyone sees. The rest — the content, the links, the recommendation you spent an hour writing — none of it matters if the subject line doesn’t get the click.
This post gives you 25 formulas you can use straight away — with templates and examples for each one. According to Barilliance’s email marketing research, the average email open rate across industries is around 20%. Small improvements to your subject lines compound significantly over time.
Dip in, find the ones that fit your style and your audience, and start testing.
If you’re still setting up your email list or welcome sequence, my welcome email examples and welcome email sequence guide cover those first.
Three Things That Make an Email Subject Line Formula Work
Before the formulas, it’s worth understanding what’s actually happening when someone decides to open an email.
Curiosity. Give them enough to be interested but not enough to be satisfied. The brain wants to close the loop — which means clicking to find out the rest.
Clarity. Sometimes people just want to know what they’re getting. “7 templates for your next blog post” works because it’s specific and immediately useful. Don’t be clever when clear works better.
Pattern interruption. When every other email uses title case and exclamation marks, a plain lowercase subject line looks like a message from a friend. It stands out by not trying to stand out.
Most good subject lines use one of these three approaches. Some use a combination. I’ve found that clarity wins most often with my own audience — but the pattern interrupt performs surprisingly well on emails about personal topics.
One More Thing: Your Preheader Text
The preheader is the short grey text that appears after your subject line in most email apps. Most people leave it as “view this email in your browser” — which is a waste.
Think of the subject line and preheader as a headline and subheadline. If your subject line asks a question, the preheader can add the stakes. If your subject line is short and punchy, the preheader can add context.
Use it. It’s free real estate that most people ignore — and fixing it is one of the quickest wins available.
The 25 Email Subject Line Formulas
Curiosity-Based
These work by leaving a gap the reader needs to fill. Used well, they’re hard to ignore. Used badly, they feel like clickbait — so make sure the email delivers on the promise.
1. The Open Loop
Formula: [Personal action] + [vague outcome]
Example: I almost deleted this email
Why it works: It raises an immediate question — why would you almost delete your own email? The reader needs to know.
2. The Challenging Question
Formula: Are you [common action] + [unexpected negative]?
Example: Are you working too hard to grow your list?
Why it works: It challenges an assumption. If there’s an easier way, people want to know what it is.
3. The Insider Secret
Formula: The [topic] secret [source] won’t tell you
Example: The email trick most marketers skip
Why it works: People like feeling like they’re getting information that isn’t widely known.
4. The Unexpected Connection
Formula: What [random thing] taught me about [topic]
Example: What a delayed flight taught me about email timing
Why it works: The unusual combination creates curiosity. It also signals a story is coming, which people tend to read.
Benefit-Driven
These are the reliable workhorses. They tell the reader exactly what they’re getting. When someone is busy and scanning their inbox, clarity often wins over cleverness.
5. The Number
Formula: [Number] [things] to [result]
Example: 7 subject line templates you can use this week
Why it works: Numbers stand out in a list of text. They promise something specific and scannable.
6. The How-To Without the Pain
Formula: How to [benefit] without [obstacle]
Example: How to grow your list without spending on ads
Why it works: It removes the biggest objection before the reader even opens the email.
7. The Quick Fix
Formula: A [time] fix for [problem]
Example: A 5-minute fix for low open rates
Why it works: Speed matters. If something takes five minutes, the barrier to trying it is low.
8. Results First
Formula: How I [specific result] in [specific time]
Example: How I went from 0 to 300 subscribers in a month
Why it works: Specific numbers are more believable than vague claims. It also signals a story with a clear outcome.
Urgency and Scarcity
Use these sparingly. If every email is urgent, none of them are. But when something genuinely is time-sensitive, these formulas do the job.
9. The Countdown
Formula: [Time] left to [action]
Example: 48 hours left to grab this
Why it works: A deadline creates a reason to act now rather than later.
10. Social Proof
Formula: [Number] people are already [doing thing] — are you?
Example: 3,000 bloggers downloaded this — here’s why
Why it works: People pay attention to what others are doing. It signals that something is worth looking at.
11. The Warning
Formula: Stop [action] before you [negative outcome]
Example: Stop sending emails before you read this
Why it works: A direct warning is hard to scroll past. The reader wants to know what mistake they might be making.
Story and Connection
These work because they make you feel like a real person rather than a brand. In an inbox full of marketing, a human voice stands out.
12. The Honest Admission
Formula: I messed up [thing] so you don’t have to
Example: I made this mistake for six months
Why it works: Vulnerability is disarming. Admitting a mistake makes you trustworthy and the email immediately interesting. This is one of my highest-performing subject line types — people are drawn to honesty.
13. The Before and After
Formula: From [starting point] to [result]
Example: From 12 subscribers to 500 in 60 days
Why it works: It maps the transformation the reader wants for themselves.
14. Behind the Scenes
Formula: A look inside [process or thing]
Example: What my email workflow actually looks like
Why it works: People are naturally curious about how others do things. “Actually” signals honesty over performance.
15. The Near-Quit Story
Formula: I almost quit [thing] until [turning point]
Example: I nearly deleted my whole list — here’s what stopped me
Why it works: It hooks with drama and promises a resolution worth sticking around for.
16. The Unexpected Lesson
Formula: What [unexpected source] taught me about [topic]
Example: What my worst email taught me about writing better ones
Why it works: It’s specific and self-aware. It signals a real story rather than a generic tip.
The Low-Key Approach
These intentionally look nothing like marketing emails. They work because they look like a message from someone you know — which is exactly the impression you want to create.
17. The Lowercase Question
Formula: [simple question in lowercase]
Example: quick question
Why it works: No capitals, no punctuation, no trying. In an inbox full of polished subject lines, this looks like a text message.
18. One Word
Formula: [single noun or question word]
Example: this?
Why it works: It’s so minimal it creates genuine curiosity. What is “this”? The reader has to open to find out.
19. The Reply
Formula: Re: [previous topic]
Example: Re: your email list
Why it works: It looks like a continuation of a conversation. Use this carefully — only in follow-up sequences where there genuinely was a previous email on that topic.
20. The Casual Reference
Formula: [thing] + (link) or (inside)
Example: that template you asked about (inside)
Why it works: It feels like someone keeping a promise rather than sending a broadcast.
Problem and Solution
These speak directly to what your reader is struggling with. When the subject line names the exact problem someone has, they feel seen — and they open.
21. The Frustration Callout
Formula: Tired of [problem]?
Example: Tired of emails no one opens?
Why it works: If the answer is yes, they’re already interested in what you have to say.
22. The Mistake Warning
Formula: Stop [common mistake] today
Example: Stop writing subject lines like this
Why it works: It’s direct and slightly provocative. The reader wants to know if they’re making the mistake.
23. The Easier Way
Formula: A much easier way to [result]
Example: A much easier way to write weekly emails
Why it works: Nobody wants to do things the hard way if there’s a better option.
24. The Contrarian Take
Formula: Why [common advice] is wrong
Example: Why posting every day is hurting your list
Why it works: It challenges what the reader thinks they know. Even if they disagree, they want to see your argument.
25. The Personalized Call
Formula: [Name], [thing] made for you
Example: [First name], I made this for you
Why it works: Personalization still works when it’s used sparingly. A name in the subject line catches the eye.
Testing Your Email Subject Line Formulas
The formulas above are starting points, not guarantees. What works for one audience might not work for another — the only way to know is to test.
Most email platforms let you run A/B split tests on subject lines. You send version A to a portion of your list, version B to another portion, and after a few hours the winner goes to everyone else.
Test one thing at a time. Subject line length, curiosity versus clarity, with or without a name — change one variable per test and you’ll actually learn something useful. I run a test on roughly every third email and the results have genuinely changed how I write subject lines.
For more on A/B testing email subject lines, HubSpot’s guide to email testing covers the technical setup.
A Word on Deliverability
None of this matters if your emails land in spam. A few things that help:
Avoid words that trigger spam filters — “free”, “cash”, “urgent”, and anything in all caps are common culprits. If you mean “free”, try “at no cost” or “on the house.”
Keep your list clean. If someone hasn’t opened an email in three months, they’re probably not going to. Removing inactive subscribers feels counterintuitive but it improves your open rates and your sender reputation — both of which help your emails land where they should.
Ask new subscribers to reply to your first email. A reply is the strongest possible signal to email providers that you’re a real person worth letting through.
What to Do Next
Pick one formula from the list above — ideally one that feels natural for your voice — and use it on your next email. Then pick a different one the time after that and see which performs better.
For more on writing emails that people actually want to read, my guide on creating a newsletter that grows your business covers the content side. And if you want to see how subject lines fit into the bigger picture of email marketing, my email marketing for beginners guide is the place to start.
