Email Subject Line Grader
Grade email subject lines with AI. Get scores, feedback, and alternatives. Embed on your website to capture qualified leads.
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Email Subject Line Grader
The average email open rate is 21.3% across all industries according to Mailchimp data. Paste your subject line to get an instant score across length, personalization, urgency, spam triggers, and mobile preview. See how your subject line compares and get specific fixes to improve open rates.
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<script src="https://calcstack.net/embed.js"
data-tool=""></script>Paste it into any HTML page. The Email Subject Line Grader renders in place. Visitor inputs, results, and contact details route to your CRM the moment they hit submit.
Email subject line graders capture marketers who are actively optimizing their email campaigns. Every graded subject line reveals their industry, audience, and campaign goals, data that email marketing agencies and tools can act on immediately.
How It Works
Paste your subject lines
Enter one or more email subject lines. Add context about your audience and campaign goal for more accurate grading.
AI grades each line
The AI evaluates each subject line on length, clarity, urgency, personalization potential, spam risk, and emotional appeal, giving a score out of 100.
Get improvement suggestions
See specific recommendations for each subject line: shorten it, add urgency, personalize it, or avoid spam trigger words. Compare scores across your variants.
Subject Line Score Scale
Who Uses This
Email Marketing Agencies
Embed to attract clients with underperforming campaigns.
SaaS Companies
Embed on marketing resources to capture growth teams.
E-commerce Brands
Embed to help merchants improve promotional email open rates.
What is Email Quality Score?
An email grader scores your email across subject line effectiveness, body structure, personalization, mobile rendering, and deliverability factors.
The Formula
Score = (Points Earned ÷ Maximum Points) × 100
Worked Example
A marketing email: subject 7/10, body 8/10, personalization 5/10, mobile 6/10, deliverability 8/10.
- Total = 7 + 8 + 5 + 6 + 8 = 34
- Maximum = 50
- Score = (34 ÷ 50) × 100 = 68%
📌 The email scores 68%, good structure but personalization and mobile rendering need improvement.
Why This Matters
Open rates
Subject line quality determines 50% of open rate variation. A 5-point score improvement can lift opens by 15-20%.
Deliverability
Emails with spam trigger words see 25% lower inbox placement. Grading catches issues before sending.
Revenue per send
Well-optimized emails generate 2-3x more revenue per recipient than poorly crafted ones.
Common Mistakes
❌ Image-heavy emails
Emails with 60%+ images get blocked by many clients and load slowly on mobile. Aim for 60/40 text-to-image ratio.
❌ No preview text
Preview text is the second most important element after subject line. Leaving it blank wastes prime real estate.
❌ Not testing across clients
An email that looks perfect in Gmail may break in Outlook. Test across the top 5 email clients before sending.
Industry Benchmarks
| Category | Good | Average | Poor |
|---|---|---|---|
| Subject Line Score | 8+/10 | 5-8/10 | Below 5/10 |
| Mobile Compatibility | 95%+ render correctly | 80-95% | Below 75% |
| Spam Score | Under 2/10 | 2-5/10 | Above 5/10 |
Source: Litmus State of Email Report 2025
Comparing static form deployments to interactive tool deployments surfaces a consistent pattern: businesses that replace static forms with interactive tools like this one see 3-5x more qualified leads, visitors volunteer their data because they get personalized results in return.
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Frequently Asked Questions
What does the email subject line grader analyze?▼
Can I grade multiple subject lines at once?▼
What are the most common email subject line mistakes?▼
How does the email subject line grader generate leads?▼
What lead intelligence does the subject line tool capture?▼
How do email tool companies convert grader users into customers?▼
Embed This AI Tool on Your Website
Every visitor who uses this tool becomes a qualified lead.