The best email signature size is about 600 pixels wide, with a logo between 120 and 200 pixels wide and every image kept to a small file. Those are rules of thumb, not standards: no mail app publishes an official “best” size. They work because they fit a desktop reading pane and shrink cleanly on a phone.
This article gives the email signature size numbers, explains why each one matters, and covers the one hard limit we can quote from a source: Gmail’s character limit.
Email signature size at a glance
- Total width: about 600 pixels or less.
- Logo: 120 to 200 pixels wide as displayed. Save the file at double that for sharp screens.
- Photo: a square, 80 to 120 pixels as displayed.
- File weight: each image in the tens of kilobytes.
- Height: keep it short, about 150 pixels or less, so it does not outweigh the message.
- Gmail limit: 10,000 characters per signature, images included.
Email signature size: the right width
Most people read email in a window between 600 and 800 pixels wide for the message body, and on a phone it is narrower. A signature wider than the window either gets cut off, scrolls sideways or shrinks the whole message. Staying at or under 600 pixels avoids all three.
Two layout decisions follow:
- Put the logo above or beside the text, not both. A logo on the left plus a photo on the right plus text in the middle is where narrow screens break first.
- Use a fixed width for the table, with percentages inside it. A table that is 600 pixels wide and shrinks on narrow screens behaves better than one with fixed-width cells all the way down.
Layouts in emailfooter use a fixed width of 600 pixels for most designs, 680 when the logo sits beside the text and 520 for the centred layout, with the contact lines in a two-column grid.
Email signature logo size
A logo of 120 to 200 pixels wide, as displayed, is enough for most companies. Any larger and it competes with your message.
There is a second number: the actual size of the file. Screens with high pixel density draw an image at twice its nominal size if it is available, and blur an image that is not. So make the file twice the display width. If the logo shows at 160 pixels wide, save it at 320 and set the displayed width to 160 in the signature.
For the format, PNG suits logos with flat colours and sharp edges. JPEG suits photographs. Some mail apps do not display SVG, so avoid it. Here is a signature at a sensible size, 600 pixels wide with a small logo and photo:
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A 600-pixel signature with a small logo and a square photo. The company and person are made up.
Photo size
A square photo of 80 to 120 pixels as displayed is typical, again saved at twice the size. Crop it to a square first so the layout does not distort the face. Circular crops are done in the layout, not in the file.
File weight
The size in kilobytes matters more than most people think. Heavy images slow the message, count against mailbox storage, and in some apps stop loading automatically on mobile data. As a rough target, keep the logo in the tens of kilobytes and the photo under about 50 kilobytes. Most image editors have an “export for web” option that does this.
Hosted images help here. A picture linked from your website is fetched when the reader opens the message, rather than being attached to every email, which keeps the message itself light. A pasted image is often attached to each one.
Height and overall email signature size
Because the signature sits at the bottom of every message, height does more damage than width. A signature taller than the message it follows makes short replies look odd, so email signature size is a question of height as well as width. Aim for four to seven lines of text and, if you use a logo or a photo, let it sit beside the text rather than above it so the block stays short.
Email signature size limits: Gmail’s character limit
Google’s help page for Gmail signatures says a signature can hold up to 10,000 characters, including images. The page is at support.google.com/mail/answer/8395 and we checked it in October 2026.
It is worth knowing what counts. The 10,000 characters include the HTML behind the signature, not only the words you see. A layout built from tables with inline styles uses far more characters than the visible text, and every link and image reference adds more. If Gmail refuses to save a long signature, trim styling first and text last.
For Outlook, Microsoft’s help page does not state a size or image-dimension limit that we could find, so we do not quote one. Test with an email to yourself.
Why dark mode belongs in a size guide
It is not about size, but it is the same kind of surprise. A logo with a transparent background and dark text disappears on a dark background. Either use a logo that has its own light background or outline, or supply a separate light version for dark mode. The editor in emailfooter shows a light and a dark preview so you can see both.
Email signature size checklist
- Total width 600 pixels or less.
- Logo 120 to 200 pixels wide, saved at double size.
- Photo square, 80 to 120 pixels wide, saved at double size.
- Each image a small file, a few tens of kilobytes.
- Four to seven lines of text.
- Alt text on every image.
- A test message to yourself in light and dark mode, on a computer and a phone.
Frequently asked questions
What size should an email signature logo be?
Around 120 to 200 pixels wide as displayed. Save the file at twice that width so it stays sharp on high-resolution screens.
What is the maximum email signature size in Gmail?
Google says 10,000 characters, including images.
How wide should an email signature be?
About 600 pixels or less.
What file size should an email signature image be?
As a rule of thumb, tens of kilobytes. There is no official limit in most apps, but smaller loads faster and is less likely to be blocked.
Should I use PNG or JPEG for my email signature?
PNG for logos and flat graphics, JPEG for photographs. Avoid SVG, which some mail apps do not display.
Can I make the signature bigger on a phone?
Not by itself. Mail apps scale the message to the screen. That is why a modest width is safer than a large one.
Keep reading
- Email signature: what it is, what to put in it and how to set it up: Everything about the email signature: what to include, how big it should be, design rules, legal lines, examples and how to set it up in Gmail and Outlook.
- Free email signature templates: ten layouts you can copy: Free email signature templates in ten layouts, from classic and executive to compact and wide, with advice on choosing one and how to get it into your mail app.
- How to add email signature in Gmail (computer and phone): How to add email signature in Gmail on a computer and on your phone, with the settings for replies, extra addresses and images, plus fixes if it will not show.
- What is an email signature? A plain explanation with examples: What is an email signature? A clear explanation of what it is, what it contains, why businesses use one and how it differs from a disclaimer or a sign-off.
Make every signature in your company match
emailfooter is a free WordPress plugin. You design the signature once, and each person adds their own details and installs it in their mail app. Prefer not to run a website? emailfooter Managed is the same software, hosted for you.