Email Signature Banner Size: The Right Dimensions for Gmail and Outlook

Quick answer: design an email signature banner to display at about 600 pixels wide and no more than 100 pixels high, then export the file at twice that size (1,200 by 200) so it stays sharp on high-resolution screens. Google's published maximum for a signature image is 100 pixels high by 1,000 pixels wide, and a whole signature of 600 pixels wide or less is a safe overall width.

A banner is the easiest part of a signature to get wrong, because it is usually designed in a tool that has no idea how email programs behave. The sizes below come from what Google and Microsoft document and from the email-testing community, and they are the same numbers used in our full email signature size guide.

What size should an email signature banner be?

• Displayed width: about 600 pixels or less. Keeping a whole signature at about 600 pixels wide or less is a safe choice, so a banner at or below that fits.
• Displayed height: 100 pixels or less. Google's guidance for Gmail signature images is 70 to 100 pixels high and 300 to 400 wide, with a maximum of 100 by 1,000.
• File size: export at twice the displayed size for sharp screens, and keep the file well under 50KB if you can, with the whole signature under about 150KB.
• Format: JPG for photographs and PNG for flat graphics or text. Avoid SVG, which many email programs don't support.

Set the width and height on the image itself

Litmus notes that Outlook does not support CSS styles for widths and heights, and if you do not set width and height attributes it shows the image at its actual size. A 1,200 pixel banner shrunk only with styling can therefore appear at full size in Outlook and push your signature off the screen. Set explicit width and height on the image (600 by 100 for the example above) and let the file be twice that.

Don't put your contact details only inside the banner

Outlook is configured by default to block automatic picture downloads, so some of your recipients will see a blank box where the banner should be. A banner works best as a promotion or a visual accent below typed details, never as the only place your name, phone or links live. We explain why in our article on image-only email signatures.

Banner or button?

A short call-to-action button in text often outperforms a banner for the same space, because it still shows when pictures are off and it can be tapped. If you do use a banner, make it one link, give it real alt text, and put it under your details.

Animated banners

Animated GIF banners are a deliberate choice, not a default. Litmus advises making the first frame carry the message, because some Outlook versions show only that frame, and they add file weight and a promotional look. Use one only when the movement earns its place.