A free email subject line length checker that shows where each phone cuts your line, and which words get cut off.
5.0(1 rating)Type your subject line and preview text. See where the Gmail app and iPhone Mail cut them on a phone and which words get cut off, then the score and the checks.
The kind of email
Your line
What you type stays in this browser. The checks run on your device.
This free email subject line length checker shows where the Gmail app and iPhone Mail cut your subject line on a phone, and which words get cut off.
It measures your line in each app's own inbox row, so a W takes more room than an i. It also scores the line against 56,262 real emails and checks it for spam rules.
Here's how long a subject line should be, what the data says, and where each inbox cuts it.
What is an email subject line length checker?
An email subject line length checker counts your subject line and shows how much of it an inbox displays before cutting it off.
How long should an email subject line be?
Long enough to say what's inside, with the reason to open in the first 35 or so characters.
Length itself didn't decide which email got more reactions. In 56,262 emails from public newsletters, when 2 subject lines from the same newsletter differed by 10 or more characters, the shorter one won 49.7% of 22,678 head-to-heads.
- Got more reactions
- 49%
- Head-to-heads
- 5,905
- Got more reactions
- 49%
- Head-to-heads
- 10,235
- Got more reactions
- 50%
- Head-to-heads
- 11,461
- Got more reactions
- 52%
- Head-to-heads
- 9,357
- Got more reactions
- 50%
- Head-to-heads
- 7,225
- Got more reactions
- 51%
- Head-to-heads
- 4,979
- Got more reactions
- 49%
- Head-to-heads
- 5,868
Half the lines were 39 characters or fewer. The middle half ran from 27 to 56 characters, and 1 in 10 went past 75.
Where each inbox cuts a subject line
What length does decide is what shows. I measured all 56,262 subject lines in the checker's phone inboxes, drawn 390 pixels wide, about the width of a recent iPhone.
- Subject lines shown in full
- 47%
- Where the rest got cut
- After about 36 characters
- Subject lines shown in full
- 65%
- Where the rest got cut
- After about 46 characters
A narrower phone cuts sooner, and wide letters like W and M use up the row faster than i and l. That's why the checker measures your line instead of counting characters.
On a laptop, Gmail puts the subject and the preview text on one line, so a long subject leaves less room for the preview.
Preview text length
Preview text shows right after the subject, as a second reason to open.
Make it long enough to fill its line. When it's short, Gmail fills the rest with the first words of your email, and the checker tells you when that happens.
The Gmail app gives it 1 line under the subject, and iPhone Mail shows up to 2.
Do emoji count as characters?
The checker counts an emoji as 1 character, the way people read it.
In the data, subject lines with an emoji got more reactions in 36% of 1,040 head-to-heads inside the same newsletter, so test one on your own list first.
Final thoughts on subject line length
Length doesn't decide who reacts: the shorter line won 49.7% of the time.
What length decides is what shows. Put the reason to open in the first 35 characters, and let the rest add detail.
Then write preview text long enough to fill its line, and check the full score and spam checks before you send.
Email Subject Line Length Checker FAQs
Questions about subject line length? Here's what to know.
An email subject line length checker counts your subject line and shows how much of it an inbox displays before cutting it off.
An email subject line should be long enough to say what's inside, with the reason to open in the first 35 or so characters.
In 56,262 real emails, the shorter of 2 subject lines won 49.7% of the time, so length alone didn't decide which email got more reactions.
How many characters show depends on the app, the phone's width and the letters, since a W takes more room than an i.
In the checker's inboxes at 390 pixels wide, the Gmail app cut real subject lines after about 36 characters and iPhone Mail after about 46.
A shorter subject line didn't win more often in our data, which counts reactions rather than opens.
When 2 lines from the same newsletter differed by 10 or more characters, the shorter one got more reactions 49.7% of the time, about a coin flip.
Preview text should be long enough to fill the line after the subject, or Gmail fills the rest with the first words of your email.
The subject line length checker tells you when your preview leaves room.
The subject line length checker counts an emoji as 1 character, the way people read it.
In 56,262 newsletter emails, subject lines with an emoji got more reactions in 36% of 1,040 head-to-heads.
Yes, the subject line length checker is free, with no sign-up.
What you type stays in your browser.
The subject line length checker is for anyone who sends email: newsletter writers, marketers, founders and creators.
The email subject line tester scores your line against real emails, and the email subject line generator writes new ones with your AI.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.
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