Your email's subject line is the gatekeeper. It doesn't matter how brilliant your email body is—if no one opens it, no one reads it. And in a world where the average professional receives 120+ emails per day, your subject line has about 2 seconds to make an impression.
The difference between a great subject line and a mediocre one can mean the difference between a 40% open rate and a 10% open rate. That's not a marginal improvement—it's the difference between getting meetings and getting ignored.
This guide gives you 50 battle-tested subject line formulas across 10 categories. Each formula comes with examples you can swipe and adapt for your own emails. Bookmark this page—you'll come back to it every time you write a cold email.
The Psychology of High-Performing Subject Lines
Before we dive into the formulas, let's understand what makes subject lines work. The best subject lines trigger one or more of these psychological levers:
- Curiosity: Makes them want to know more
- Relevance: Directly relates to their role, company, or interests
- Specificity: Contains concrete details that stand out from generic emails
- Urgency: Creates a sense of timeliness (without being manipulative)
- Personalization: Shows you know who they are
- Value: Promises something useful or beneficial
The best subject lines combine 2-3 of these elements. Now let's see them in action.
Category 1: The Personalized Reference
These subject lines reference something specific about the recipient—their content, company, or activity. They immediately signal "this isn't a mass blast."
Formula 1: "[Their Content] + Observation"
- Your LinkedIn post on hiring
- Loved your podcast episode with Jason Lemkin
- Your take on product-led growth
Formula 2: "[Company Name] + Topic"
- Quick idea for Stripe's outbound
- Notion + content strategy
- Thought about Figma's sales team
Formula 3: "Saw [Specific Activity/Achievement]"
- Saw you're hiring for VP of Sales
- Noticed the new product launch
- Saw your talk at SaaStr
Formula 4: "Congrats on [Achievement]"
- Congrats on the Series B!
- Congrats on hitting 100K users
- Congrats on the new role
Formula 5: "[Mutual Connection] suggested I reach out"
- Mike Chen suggested we connect
- Sarah mentioned you'd be good to talk to
- Following up on David's intro
Category 2: The Question
Questions create an open loop in the reader's mind. They naturally want to answer—or at least find out what the question is about.
Formula 6: "Quick question about [Topic]"
- Quick question about your tech stack
- Quick question about outbound
- Quick question about the sales team
Formula 7: "[Problem] keeping you up at night?"
- SDR ramp time keeping you up at night?
- Pipeline still a problem?
- Email deliverability issues?
Formula 8: "Is [Assumption] still a priority?"
- Is outbound still a priority?
- Is scaling the team still on the roadmap?
- Still focused on enterprise deals?
Formula 9: "Can I ask you something?"
- Can I ask you something? (use sparingly—high open rate but can feel clickbaity)
Formula 10: "Have you considered [Alternative Approach]?"
- Have you considered outbound as a channel?
- Ever thought about video prospecting?
- Considered a partner program?
Category 3: The Curiosity Gap
These subject lines create intrigue by hinting at valuable information without giving it all away. The recipient has to open to find out more.
Formula 11: "Something I noticed about [Company]"
- Something I noticed about your website
- Something interesting about your sales page
- Noticed something in your cold emails
Formula 12: "This might sound crazy, but..."
- This might sound crazy, but...
- Weird idea for you
- Unconventional thought
Formula 13: "[Number] + [Intriguing Promise]"
- 3 things your competitors are doing
- 2 ideas that might help
- 1 quick observation
Formula 14: "You're probably doing [X] wrong"
- You're probably doing cold email wrong
- Most companies mess this up
- The mistake I see with outbound
Formula 15: "Don't open this email"
- Don't open this email (use very sparingly—pattern interrupt that can backfire)
Category 4: The Social Proof
These subject lines leverage the credibility of other companies, results, or relationships to establish trust before they even open.
Formula 16: "How [Similar Company] achieved [Result]"
- How Gong cut sales cycles by 40%
- How HubSpot scaled their SDR team
- How Notion's outbound strategy works
Formula 17: "[Number] + [Timeframe] for [Similar Company]"
- 40% reply rates for Salesforce's team
- 3x pipeline in 6 months for Dropbox
- 30% faster ramp time at Zoom
Formula 18: "Working with [Impressive Client/Name]"
- Working with companies like Stripe
- Just wrapped up with the Atlassian team
- Helped Shopify's sales org
Formula 19: "[Industry] trends from [Number] companies"
- Sales trends from 500+ B2B companies
- What we learned from 1,000 cold email campaigns
- Benchmarks from 200+ SaaS sales teams
Formula 20: "Fellow [Shared Experience/Group]"
- Fellow YC founder here
- Another sales leader in B2B SaaS
- Fellow Miami transplant
Category 5: The Value Proposition
These subject lines lead with the benefit—what the recipient stands to gain by opening and engaging.
Formula 21: "Idea to [Achieve Specific Result]"
- Idea to double your reply rates
- Idea for faster pipeline generation
- Idea to reduce SDR ramp time
Formula 22: "[Solve Problem] in [Timeframe]"
- Fix your deliverability in a week
- Better meetings in 14 days
- Ramp reps in 60 days, not 90
Formula 23: "The [Adjective] way to [Achieve Goal]"
- The lazy way to book more meetings
- The faster way to qualify leads
- The easier way to personalize at scale
Formula 24: "[X] without [Y]"
- More meetings without more SDRs
- Scale outbound without sounding robotic
- Better emails without more time
Formula 25: "What if [Desirable Outcome]?"
- What if outbound actually worked?
- What if you could 2x replies?
- What if new reps ramped in 30 days?
Category 6: The Short and Simple
Sometimes less is more. Short subject lines stand out because they're unusual—most people write long, descriptive subject lines.
Formula 26: "Quick [Request]"
- Quick question
- Quick idea
- Quick thought
Formula 27: "[Topic]?"
- Outbound?
- Sales hiring?
- Coffee?
Formula 28: "[First Name]"
- Sarah
- Hey Mike
- Hi David
Formula 29: "Re: [Topic]"
- Re: sales strategy
- Re: our conversation
- Re: the team
(Note: Only use "Re:" if there was an actual prior conversation. Faking thread replies is deceptive and will backfire.)
Formula 30: "[One Word]"
- Thoughts?
- Interesting
- Timing
Category 7: The Timely/Urgent
These subject lines create a sense of timeliness without being manipulative. They reference real deadlines, seasons, or relevant timing.
Formula 31: "[Time Period] planning"
- Q2 planning
- 2026 priorities
- End of year push
Formula 32: "Before [Event/Deadline]"
- Before your board meeting
- Before you hire more SDRs
- Before the conference
Formula 33: "[Recent Event] follow-up"
- SaaStr follow-up
- After the product launch
- Post-funding chat
Formula 34: "This week"
- This week only
- Before this week ends
- Quick chat this week?
Formula 35: "Time-sensitive"
- Time-sensitive idea
- Before you decide
- Relevant for right now
Category 8: The Pattern Interrupt
These subject lines break expectations and stand out by being different from typical business emails.
Formula 36: "[Unexpected Emoji]"
- 🎯 Quick idea
- ☕ Coffee chat?
- 🤔 Thought experiment
Formula 37: "[Lowercase, casual]"
- hey
- quick thing
- random idea
Formula 38: "[Honest/Self-Deprecating]"
- Probably not for you, but...
- Feel free to ignore this
- Last email, I promise
Formula 39: "[Intriguing Statement]"
- I was wrong about your company
- Weird request
- Not the typical cold email
Formula 40: "[Pop Culture/Humor Reference]"
- The Office GIF you need to see
- Found Michael Scott's sales playbook
- No pressure like those emails about your car warranty
Category 9: The Follow-Up Specific
When following up on a previous email, these subject lines work better than "Re: [original subject]."
Formula 41: "Bumping this up"
- Bumping this up
- Floating this back up
- Quick resurface
Formula 42: "Did I catch you at a bad time?"
- Did I catch you at a bad time?
- Bad timing?
- Not the right moment?
Formula 43: "[New Information]"
- New case study on [topic]
- Update since we last connected
- New data you might find interesting
Formula 44: "Still [Interested/Relevant]?"
- Still thinking about outbound?
- Still a priority?
- Still interested in chatting?
Formula 45: "Closing the loop"
- Closing the loop on this
- Should I close your file?
- One last note
For complete follow-up strategies, see our guide: 7 Follow-Up Email Templates That Actually Work.
Category 10: The Newsletter/Content
If you're sending newsletters or content emails, these formulas work well for recurring sends.
Formula 46: "[This Week's/Today's] [Topic]"
- This week's best cold emails
- Today's sales tip
- Friday's content roundup
Formula 47: "[Number] [Things] from [Time Period]"
- 5 cold email wins from this week
- 3 templates from January
- 10 subject lines that crushed it
Formula 48: "The [Adjective] [Topic] issue"
- The no-BS sales newsletter
- The short version
- The actually useful email tips
Formula 49: "[Trending Topic] + Your Take"
- AI in sales: what's real and what's hype
- The cold email debate, settled
- LinkedIn's new features: worth it?
Formula 50: "[Exclusive/Inside] + [Topic]"
- Inside: how top reps write cold emails
- Exclusive: 2026 sales benchmarks
- Behind the scenes: building a sales playbook
Subject Line Best Practices
Now that you have 50 formulas, here are some universal best practices to apply:
Length Matters (But Not How You Think)
The conventional wisdom is "keep subject lines under 50 characters." The data tells a more nuanced story:
- 1-5 words: Highest open rates (curiosity, stands out)
- 6-10 words: Best for conveying value proposition
- 11+ words: Gets cut off on mobile, but can work if front-loaded
The key: put the most important words first. Mobile email clients cut off around 30-40 characters.
Personalization Placement
If you're personalizing, put the personalized element first. Compare:
- ✅ "Sarah—quick question about Stripe"
- ❌ "Quick question about Stripe, Sarah"
They see "Sarah" immediately and know it's not a blast.
Avoid Spam Triggers
These words and patterns increase the likelihood of landing in spam:
- ALL CAPS
- Excessive punctuation!!!
- "Free," "Limited time," "Act now"
- Money symbols ($$$) or numbers (100% guaranteed)
- Re: or Fwd: when there's no prior conversation
For more on protecting your email reputation, check out email privacy best practices.
Test and Iterate
What works for one audience won't work for another. Always:
- A/B test subject lines when possible
- Track open rates by subject line formula
- Retire formulas that underperform
- Double down on what works
Most email tools (Mailchimp, Apollo, HubSpot) have built-in A/B testing. Use it.
Putting It All Together
Let's look at how to apply these formulas to a real cold email campaign targeting VPs of Sales at SaaS companies:
Email 1 (Initial):
- Option A: "Your LinkedIn post on sales hiring" (Personalized Reference)
- Option B: "Idea for [Company]'s SDR ramp time" (Value Proposition)
- Option C: "Quick question about outbound" (Question)
Email 2 (Follow-up #1):
- Option A: "Floating this back up" (Short and Simple)
- Option B: "How Gong cut ramp time by 40%" (Social Proof)
Email 3 (Follow-up #2):
- Option A: "Something I noticed about your job postings" (Curiosity)
- Option B: "Bad timing?" (Follow-Up Specific)
Email 4 (Breakup):
- Option A: "Should I close your file?" (Follow-Up Specific)
- Option B: "Last email, I promise" (Pattern Interrupt)
Key Takeaways
Let's wrap up with the essential principles:
- Your subject line's only job is to get the email opened. Don't try to make the sale in the subject line.
- Personalization beats cleverness. A subject line that references something specific about them will outperform a "clever" generic line.
- Curiosity and value are your best tools. Make them want to know more, or promise them something useful.
- Match your tone to your audience. Casual and creative works for startups; professional works for enterprise.
- Test, measure, iterate. Let data, not intuition, guide your subject line strategy.
Save this guide and refer back to it every time you write a cold email. With 50 formulas at your disposal, you'll never stare at a blank subject line again.
Now go write an email that gets opened.
Related guides: