Features / Cold email subject line grader
Cold email subject line grader: what it does and how to use it
Updated November 7, 2026. Our tool page and the pages cited here were read that day. Data through October 18, 2026.
The free Sales.co cold email subject line grader scores a subject line against replies from 934,469 prospects emailed from October 2025 to October 2026. It checks four patterns that went with more human replies, from the prospect's first name to word count, and gives a grade from A to D.
This page is for founders and sales reps who write their own cold email. The grader is here, free. If you would rather not write the email at all, our done-for-you cold email starts at $2,000 a month.
Quick picks: what are you doing?
| You have | Use | Why |
|---|---|---|
| One subject line to check before sending | Subject line grader | It scores the line on reply data from cold sends |
| No ideas yet | Cold email subject line examples | Lines to adapt, then grade them |
| A newsletter or promo email | CoSchedule Email Subject Line Tester | It scores length, word balance, skimmability and sentiment (read November 7, 2026) |
| A draft body to check | Email spam checker | It flags words and formatting in the email itself |
| The subject line sorted but no list | Industry email lists | $295 one time, CSV |
What the grader checks
It checks four patterns, each of which went with more human replies in the sending data, both overall and with the largest sending account removed: the prospect's first name in the line, five to seven words, 30 characters or fewer, and a capital first letter instead of all lowercase. Meeting all four is an A, three is a B, two is a C and fewer is a D. The first-name check runs only when you type the prospect's first name.
How to grade a subject line in four steps
- Open the grader and type your subject line.
- Add the prospect's first name and company if you have them, so those checks can run.
- Press Grade it. Read which patterns your line met and which it missed.
- Rewrite the missed ones and grade again. You are done when you reach an A, or a B you like.
What the data says
The biggest gap in 934,469 prospects is the first name. Lines with it got 0.89% human replies and lines without it 0.57%, 1.5 times as many (340,437 against 551,141 prospects, data through October 18, 2026). With the largest sender removed the gap holds at 0.77% against 0.55%. The grader's own page shows the full table, so we do not repeat it here.
When to use it
Use it on the first email of a sequence, the one that carries the subject line the recipient sees. For the next steps, see the best time to send cold email and the follow-up email templates.
What it costs
The grader is free and needs no signup. A subject line is one part of a campaign; the done-for-you service covers the list, the writing, the sending and the follow-ups from $2,000 a month.
Sources
- Reply rates, patterns, grade rules and n: the grader page, read November 7, 2026 (data/subject-patterns.json, through October 18, 2026).
- CoSchedule: coschedule.com/email-subject-line-tester, read November 7, 2026.
- Sales.co price: pricing page, read November 7, 2026.
FAQ
How does the subject line grader score a line?
It counts how many of four patterns your line meets: the first name, five to seven words, 30 characters or fewer and a capital first letter. Each went with more human replies in 934,469 prospects of Sales.co sending data.
Is the grader free?
Yes, free with no signup.
Does a first name in the subject line help?
In this data, yes: 0.89% human replies with it against 0.57% without, across 340,437 and 551,141 prospects, data through October 18, 2026.
Is this data from newsletters or cold email?
Cold email. It is Sales.co sending data from 60 sending workspaces, one first email per prospect.