SignguinThe best email signature size is no wider than 600 pixels and about 100 to 200 pixels tall. Inside that space, a logo works at about 120 to 180 px wide, a headshot at 80 to 100 px square, social icons at 20 to 24 px, and a banner at up to 600 x 100 px. Text reads best at 13 to 14 px, with your name at 16 to 18 px. Save every image at twice the size it will display, and keep each file under roughly 50 KB.
Those are the short answers. The rest of this guide explains where each number comes from, where the experts disagree, and what actually happens in Outlook, Gmail and on phones when you go bigger.
Email signature size cheat sheet
| Element | Display size (what people see) | Upload at (2x for sharp screens) | File size | Why |
|---|---|---|---|---|
| Whole signature width | 600 px maximum (400 to 500 px is safer for phones) | n/a | n/a | Fits desktop reading panes; phones show about 360 to 414 px |
| Whole signature height | 100 to 200 px | n/a | n/a | Stays a sign-off, not a second email |
| Logo, wide | 120 to 180 px wide, up to 60 px tall | 240 to 360 px wide | under 30 KB | Readable without dominating the name |
| Logo, square | 60 to 80 px | 120 to 160 px | under 20 KB | Square logos look bigger at the same width |
| Headshot | 80 to 100 px square (or round) | 160 to 200 px | under 30 KB | Face recognizable on a phone |
| Banner | up to 600 x 100 px | up to 1200 x 200 px | under 50 KB | Matches the max width; Gmail's max image height is 100 px |
| Social icons | 20 to 24 px each, 8 to 12 px apart | 40 to 48 px | under 5 KB each | Clear, still tappable |
| Text | 13 to 14 px (10 to 11 pt) | n/a | n/a | iPhones enlarge anything under 13 px |
| Your name | 16 to 18 px, bold | n/a | n/a | One clear visual anchor |
| Lines of text | 3 to 6 | n/a | n/a | Repeats in every reply |
| All images together | n/a | n/a | under 100 KB | Light emails, quick loading |
| Gmail code limit | 10,000 characters | n/a | n/a | Gmail's hard limit, images included if embedded |
|
Why 600 pixels is the maximum width
Six hundred pixels has been the standard width for email designs for years, and it works for signatures for the same reason: it fits inside the reading pane of desktop email apps without a sideways scroll bar, even with a folder list and message list open beside it.
Google is more conservative for single images. Gmail's help center recommends a signature image of 300 to 400 pixels wide and 70 to 100 pixels high, with a maximum of 100 px high by 1000 px wide. Google doesn't say whether that maximum refers to the file or the displayed size, so if you upload through Gmail's own editor, resize the file first and then use the editor's Small, Medium, Large or Original size options.
The bigger constraint is phones. StatCounter's September 2026 data for the US shows the most common phone screens are 414, 390, 384, 393, 360 and 402 pixels wide (in the screen units web pages use). Subtract the mail app's margins and you have roughly 330 to 380 px for your signature.
What happens to a 600 px signature on a 390 px phone depends on the app: some scale the whole email down, others let it run off the edge so the reader scrolls sideways. Scaling 600 px to 360 px shrinks everything to 60%, which turns 13 px text into the visual equivalent of 8 px.
Where sources disagree: published guides recommend anything from 320 px to 700 px as the maximum. One suggests 320 px for a mobile-heavy audience; others allow 650 px for banners. Our default: never above 600 px, and design the important part (name, phone, email) so it fits in a column of about 350 px. A stacked layout, with the logo above the text instead of beside it, does that naturally.
|
Height: keep it between 100 and 200 pixels
Height is less about technical limits and more about proportion. Your signature appears under every email and every reply, so a 300 px tall block can be taller than the message itself. Most size guides land on 150 to 200 px as the comfortable maximum, and Gmail's 100 px maximum image height fits inside that.
If your design needs more height, that's usually a sign of too much content: two phone numbers, a full address, a quote, a banner and a legal notice. Cut lines before you shrink fonts.
Email signature logo size
Aim for 120 to 180 px wide and no more than about 60 px tall for a wide logo, or 60 to 80 px for a square one.
The reasoning: your logo should be recognizable, but your name is what people need to read. A logo wider than about 200 px starts competing with the text, and on a phone it pushes the contact details down or sideways.
Two practical tips:
- Trim the empty space. Many logo files have wide transparent margins. A 300 px file with 80 px of padding on each side shows a logo that looks much smaller than you planned. Crop tight to the artwork.
- Square and round logos look larger than wide ones at the same width, so give them less room.
Where sources disagree: published guides (checked October 2026) recommend anything from 50 x 50 px to 300 px wide. Most of the gap comes from describing different logo shapes. Our numbers split the difference by shape rather than picking one size for everything.
Signguin trims the logo it finds on your website and stores it at twice its display width, so you don't have to crop or resize anything yourself.
Headshot and photo size
Use 80 to 100 px square, displayed square or cropped to a circle, and upload it at 160 to 200 px.
Below about 70 px, a face stops being recognizable on a phone, which defeats the point of including it. Above about 120 px, the photo becomes the tallest thing in the signature and sets its height. Crop close: head and shoulders, with the face filling most of the frame. A wide shot of you in front of an office shrinks to a dot.
A JPG at 80 to 85% quality keeps a 200 x 200 px headshot under 30 KB.
Email signature banner size
A banner works at up to 600 px wide and up to 100 px tall, uploaded at up to 1200 x 200 px. Match its width to the rest of your signature so the edges line up.
Keep the message to one line of text plus one call to action, and make the text big enough to read at phone size: a 600 px banner scaled to 360 px loses 40% of its size, so text that's 14 px in the design ends up around 8 px on screen.
Never put essential information only in a banner. Classic Outlook for Windows blocks automatic picture downloads by default, according to Microsoft, so many recipients see an empty box until they click "Download Pictures."
|
Social media icon size
Use 20 to 24 px per icon, with 8 to 12 px of space between them, and upload them at 40 to 48 px.
Smaller than 20 px and the logos turn into colored dots. Bigger than 24 px and five icons in a row become the loudest part of your signature. The spacing matters as much as the size: on a phone, icons crammed together are easy to mistap.
Use PNG icons, not SVG (see formats below). Signguin generates its social icons as PNG files in your brand color for this reason.
Why images should be uploaded at 2x and shown at 1x
Most phones, Macs and many Windows laptops have high-density screens that pack two or three physical pixels into each pixel of a layout. A logo saved at exactly 150 px wide gets stretched across 300 physical pixels and looks soft. Save it at 300 px wide, tell the email to show it at 150 px, and it stays crisp.
The "tell the email" part is where signatures go wrong. There are two ways to set an image's size in HTML: with CSS (style="width:150px") or with attributes (width="150" height="50"). According to caniemail.com's testing, classic Outlook for Windows doesn't support CSS width on images, nor on div, p or span elements. It does honor the width and height attributes. So an image sized only with CSS appears in Outlook at its full file size: your 300 px logo shows at 300 px.
The safe rule: every signature image gets fixed width and height attributes that match the display size.
Three more details:
- Don't bother with 3x. It roughly doubles the file size compared with 2x, and at reading distance few people notice the difference on a small logo.
- Embedded images can ignore the width attribute. caniemail notes that Apple Mail on Mac ignores the width attribute on images embedded in the email (as opposed to hosted online). An embedded 2x image can show at double size there. Hosted images avoid this.
- Classic Outlook's editor rescales by DPI. If you insert a picture through classic Outlook's signature editor, it reads the DPI value in the file and rescales the image as if it were 96 DPI, then compresses it when you send, according to Microsoft MVP Robert Sparnaaij. A file saved at 150 DPI shrinks to about two-thirds of its size and gets blurry. In Outlook for Microsoft 365, turn on File > Options > Mail > Editor Options > Advanced > Do not compress images in file.
Email signature file size (KB)
Keep each image under about 30 to 50 KB, social icons under 5 KB each, and the whole set under 100 KB.
How much file size matters depends on how the images travel:
- Embedded images are packed into every email you send. A 200 KB signature on 40 emails a day is 8 MB of extra data daily, and many email apps list embedded images as attachments (the familiar image001.png).
- Hosted images are stored on a server and loaded when the email is opened. They don't add to the email's size, but heavy files still load slowly on a weak phone connection.
Where sources disagree: Robert Sparnaaij recommends 10 KB or less for embedded images and under 25 KB for hosted ones. Other guides (checked October 2026) say under 40 KB, under 50 KB per image with 100 KB in total, or up to 150 KB in total. The strict numbers come from an Outlook expert thinking about embedded images, the looser ones from designers thinking about hosted ones. If your images are hosted, 30 to 50 KB per image is fine. If they're embedded, aim for the strict end.
To get there: export PNG logos with a limited color palette, compress JPG photos to around 80% quality, and don't upload a 2000 px photo and let the email shrink it.
Signguin hosts the images in every signature it makes, so they are linked rather than packed into each email (classic Outlook for Windows can still embed linked images when it sends, in some setups; see Outlook signature not showing), and they don't break if your website changes later.
Gmail's 10,000 character limit
Gmail allows up to 10,000 characters in a signature, and that includes the HTML code behind the formatting, not just the visible text. Google's help page adds that an image also counts toward the limit. That matters when an image is pasted into the signature as embedded data instead of a link: a single small logo stored that way can use up thousands of characters on its own, and Gmail refuses to save the signature.
A hosted image only costs the length of its web address. That's one reason designed signatures with hosted images fit comfortably, and every signature Signguin creates is built to stay within Gmail's 10,000-character limit. For the install steps, see how to change your Gmail signature.
Email signature font size
Use 13 to 14 px for contact details and 16 to 18 px for your name. In apps that measure in points, such as classic Outlook and Word, that's about 10 to 11 pt for details and 12 to 14 pt for your name (1 pt is 1.33 px on a standard screen).
Why not smaller? iPhones enlarge text in emails that is smaller than 13 px, as CodeTwo's knowledge base documents (updated July 2026). A signature designed at 11 px suddenly shows larger on iPhone than on desktop, and the layout shifts. Starting at 13 px avoids the jump.
Why not bigger? Dartmouth's email guidelines set a 16 px minimum for body text, and that's sensible for the message itself. A signature is secondary information, though, and at 16 px a five-line contact block outweighs the email above it. Keep your details slightly smaller than your message text, and let the name carry the emphasis through size and weight.
Line height of about 1.4 to 1.5 keeps the lines readable without spreading the signature taller than it needs to be.
Email signature font: which fonts are safe
Use a font that's installed on nearly every computer and phone, such as Arial, Helvetica, Verdana, Georgia or Times New Roman. Gmail and older Outlook versions ignore downloadable web fonts, and older Outlook can even drop such text to Times New Roman, so put brand typography in the logo image and keep contact details in a standard font. Which fonts ship with Windows, Mac, iPhone and Android, plus stacks and pairings, are in our guide to the best font for an email signature.
Image formats: PNG, JPG, GIF, SVG and WebP
| Format | Use it for | Notes |
|---|---|---|
| PNG | Logos, icons, anything with sharp edges or transparency | The safe default for signatures |
| JPG | Photos and headshots | Smaller files for photos; no transparency |
| GIF | Simple animation, sparingly | Classic Outlook for Windows shows only the first frame; Outlook with a Microsoft 365 account plays it 3 times and stops (caniemail) |
| SVG | Avoid | Not shown in Outlook 2007 to 2016 for Windows; Gmail on the web only began showing it in caniemail's September 2026 test, converted to PNG |
| WebP | Avoid | Not shown in any tested Outlook for Windows version |
SVG is the format web designers reach for first, which is why it causes so many broken signatures. Support has improved, but it's still patchy across the apps your recipients use, so PNG is the right choice for logos and icons in 2026.
Dark mode: make sure your logo survives
Many people read email in dark mode. Email apps darken backgrounds and recolor text, but they leave images alone, so a transparent PNG logo with dark lettering can nearly disappear on a dark gray background. The fix has to be in the image: put the logo on a small white or light background with some padding, or add a thin light outline around dark lettering, and avoid pure black text for anything important. Signguin's preview has a light and dark mode toggle, and its "White box behind logo" option builds the white tile into the logo image itself. App-by-app behavior and a 10-minute test are in our email signature dark mode guide.
What happens on phones
On a phone, your signature competes with about 360 to 414 px of screen. Three things decide whether it holds up:
- Width. A signature wider than the screen is either shrunk or scrolls sideways. Narrow, stacked layouts avoid both.
- Side-by-side columns. A logo-left, text-right layout that needs 550 px won't fit. Email-safe signatures use tables, which keep the columns side by side and shrink rather than stack, so a narrow design matters more than responsive tricks.
- Tap targets. Phone numbers and email addresses should be real links, and icons need enough space between them.
Preview on an actual phone before you install. Signguin shows a phone-width preview as you edit.
How to check your signature's size in 5 minutes
- Send a test to a Gmail address, an Outlook address and your phone.
- Open it in dark mode on at least one of them.
- Check the images: sharp on your phone (2x), the same size in Outlook as elsewhere (width and height attributes), no image001.png attachments (hosted, not embedded).
- Read it at arm's length on your phone. If you squint at the phone number, the text is too small or the signature too wide.
- Count the lines. More than six lines of text usually means something can go.
If images look broken or turn into attachments in Outlook, our guide to Outlook signatures not showing goes through each cause.
Get the sizes right without measuring anything
You can apply every number in this guide by hand with an image editor and some HTML. Or you can let a generator handle it.
Signguin is a free email signature generator that does the sizing for you: logos are trimmed and stored at 2x, social icons are PNG files in your brand color, every image has fixed dimensions and is hosted by Signguin, and every signature fits Gmail's 10,000-character limit. You preview on phone and desktop, in light and dark mode, then install it straight into Gmail or copy it into Outlook, Apple Mail and others. The free plan includes 3 designs with no sign-up; Premium adds a photo, banners and all 23 designs. Signguin is built for individuals and small businesses, so it doesn't offer team management or click analytics.
Works in Gmail, Outlook & Apple Mail
Browse more layouts in our email signature templates, or see what to put in each line in our guide to a professional email signature.
FAQ
What is the best size for an email signature?
Keep the whole signature no wider than 600 px and about 100 to 200 px tall. On phones, which show roughly 360 to 414 px, a narrower or stacked layout of 400 to 500 px reads better. Inside that, use a logo of about 120 to 180 px wide, a headshot of 80 to 100 px and social icons of 20 to 24 px.
What size should my email signature logo be?
Show a wide logo at 120 to 180 px wide and up to about 60 px tall, or a square logo at 60 to 80 px. Upload the file at twice that size so it looks sharp on high-density screens, trim any empty margins first, and set fixed width and height attributes so Outlook for Windows displays it at the intended size.
What font size should an email signature be?
Use 13 to 14 px (about 10 to 11 pt) for contact details and 16 to 18 px for your name. iPhones enlarge email text under 13 px, which can shift your layout. Stick to fonts installed everywhere, such as Arial, Verdana, Tahoma or Georgia, because Gmail and classic Outlook for Windows don't load custom web fonts.
How many KB should an email signature be?
Keep each image under roughly 30 to 50 KB, icons under 5 KB, and all images together under 100 KB. If your images are embedded in the email rather than hosted online, aim lower: Outlook expert Robert Sparnaaij suggests 10 KB per embedded image, because embedded images add their full weight to every message you send.
What is the character limit for a Gmail signature?
Gmail allows up to 10,000 characters per signature, and Google says images count toward that limit. Images pasted in as embedded data can use thousands of characters each, so a designed signature can hit the limit quickly. Hosted images only count as the length of their web address, which keeps designed signatures well under the limit.
What size should an email signature banner be?
Up to 600 px wide and 100 px tall, uploaded at up to 1200 x 200 px, and under about 50 KB. Match the width of the rest of your signature, keep it to one short message, and never put essential information only in the banner, because many recipients' email apps block images until they click to download them.