Email Subject Lines Template
Generate A/B test email subject lines with AI in Google Sheets. Free =GPT() template: five variants per email under 50 characters, plus preview text.
Stop shipping campaigns with one untested subject line: each row takes an email’s offer and audience and returns five distinct variants plus matching preview text, ready for your ESP’s A/B slot.
What you need in your sheet
| Column | Content |
|---|---|
| A | Email body or offer summary |
| B | Audience segment |
| C | Angle to test (curiosity, urgency, benefit, social proof) |
| D | Generated subject line variants |
| E | Generated preview text |
The formula
In D2, then drag down:
=GPT("Write 5 email subject lines, numbered, each under 50 characters with the key words first. Angle: "&C2&". Sentence case, no ALL CAPS, no stacked punctuation, no spam-bait words like 'FREE!!!'.", "Email: "&A2&". Audience: "&B2)
In E2 for the preview text:
=GPT("Write email preview text under 90 characters that extends — not repeats — the subject line's idea and gives one concrete reason to open.", A2)
Variations: duplicate the row with a different angle in C to test curiosity vs. benefit across the same email, or keep your brand-voice rules in $G$1 and prepend them with =GPT($G$1&" "&C2, A2).
Get started
- Install GPT for Sheets from the Google Workspace Marketplace (free tier included, no API keys needed).
- Paste each campaign’s offer summary into column A and pick an angle in C.
- Drag the formulas down, then use Replace all GPT formulas with results in the sidebar and load your favorites into the A/B test.
Full guide: GPT for Sheets documentation.
FAQ
Why five variants per email?
Because the point is testing, not a single “perfect” line. Five variants on different angles — curiosity, benefit, urgency — give you a real A/B pool per campaign; keep the two you like and let your ESP split-test them.
Will the subject lines get past spam filters?
No tool can guarantee deliverability — sender reputation and list quality matter far more than wording. What the prompt does do is avoid the classic trigger patterns: ALL CAPS, stacked exclamation marks and shouty “FREE!!!” phrasing.
Why the 50-character cap?
Mobile inboxes truncate subject lines at roughly 30–40 characters, and desktop clients around 60. Fifty keeps the whole line visible almost everywhere; the prompt front-loads the key words so even a hard cut still reads.