Email Subject Line Tester

How much of a subject Gmail shows

On a computer, Gmail shows the subject and then the first words of your email on one line, and the width of your window decides where that line ends. By the tester's count, an unread email shows about 99 characters of our sample subject in a 1440-pixel window, and about 39 at 1024 pixels. So put the words that matter first.

Gmail doesn't stop at a set number of characters. It stops when the line is full, so a subject with narrow letters like i and l fits more than one with wide letters like m and W. Unread emails have a bold subject, which takes more room.

The sample is the tester's example made longer: it starts “Maximiliano, your March invoice is ready: here is what changed since February”.

If your email opens with “Hi Maximiliano,” that greeting is what people see after the subject. They already know their name. A first sentence that says what the email is about makes better use of the space.

How we measured it

We measured Gmail in Chrome on a Mac on October 20, 2026, with the default layout: the left menu open and no reading pane. We read the width of the subject column of the inbox at six window widths. The other columns always took 746 pixels, so the column for the subject and the first words is the window width minus 746 pixels. Take off 10 pixels of padding and you get the room for text.

Gmail shows subjects in the Google Sans font at 14 pixels, in bold when the email is unread. The tester adds up the width of each letter in that font. We checked it on a draft, which Gmail lists in regular weight: Gmail showed the first 105 characters of a 132-character test subject in a 1440-pixel window, and the tester cuts it at the same place. For unread emails the tester uses the bold letters of the same font; we didn't check a bold subject in Gmail.

The numbers are for that default layout. A reading pane, a closed menu, or labels and attachment icons in the row change the room. Emoji and letters outside the Latin alphabet are estimates, and the tester says so.

Test it with your markers filled in

In your draft, a marker like {{First name}} is 14 characters, but each person sees their own name. YAMM puts each row's value from your sheet in place of the marker, in the subject too. So test the subject with a real value, and with a long one.

Take the tester's example, “{{First name}}, your March invoice is ready: what changed and what to do next”. With “Al” it's 65 characters, with “Maximiliano” 74. In a 1024-pixel window the tester shows about 39 of them either way: Al's line stops in the middle of “what changed”, Maximiliano's in the middle of “ready”. At 1280 pixels both subjects fit, but Maximiliano leaves no room for the email's first words, while Al still shows “Hi Al, her” after the subject.

Before you send, YAMM's test email fills the markers from the first visible row of your sheet, so you see one real subject in your own inbox.

What the checks mean

• Re: or Fwd: at the start. Google's email sender guidelines say not to start a subject with Re: or Fwd: unless the email really is a reply or a forward.
• Capitals and exclamation marks. YAMM's help lists capital letters and exclamation marks among the things that may trigger spam filters.
• A marker with a missing brace. YAMM reads markers written as {{First name}}, <<First name>> or $%First name%. If the tester flags one, fix it before you send.

No score, and no list of “spam words”. Google and the US Federal Trade Commission ask one thing of a subject: that it's accurate and not misleading. Our guide to why emails go to spam covers what does matter.

Need ideas for a subject first? Try the AI subject line generator. To switch a subject between sentence case and title case, use the subject line capitalization tool.

Questions about subject lines