Email signature size is more important than you might think. Ordinarily, most experts recommend that a signature can be any size you wish it to be. However, choosing any email signature size doesn’t take into account the prevalence of mobile devices. What works on a desktop PC/Mac may not work on a smartphone.

With this in mind, we have a clear set of email signature size guidelines you should use so that any template will always render correctly on all devices.

Using the right email signature size

Both memory requirements and visible size can impair the utility of an HTML email signature. Notice the word ‘utility’, and not ‘quality’; the appearance of the signature may be the same, but it just won’t be opened by most email clients.

Any quality gained by a high-resolution image will be lost as it shrinks to fit in the signature. For example, if an image file is 6MB in size, the email signature size will be very large and will take too long to load in many email clients.

Try to keep images to a file size of below 50kb. The bigger the email signature image size is, the longer it will take for your message to be sent and received by recipients.

If an email signature image size is too large, it can become very distracting for a recipient. It can even end up overpowering the actual content of the email itself. However, making images too small can be just as bad as recipients will find them hard to see. Recipients will not click on a promotional banner if they can’t see it properly.

For best results, images should be the width of a full-screen window. This is so it shrinks to fit any smaller reading pane instead of stretching to accommodate larger windows and losing its definition.

Always build your email signature template in HTML rather than using a program like Microsoft Word. If you don’t, email clients might render images incorrectly.

Mobile email signature size

Any text should be large enough to read on a smartphone’s smaller screen. However, remember that the predominantly landscape shape of an email when read on a desktop conflict with the typically portrait layout of a smartphone screen.

For mobile users, we recommend that the email signature dimensions are 320 pixels in width. This is because mobile device screen sizes are typically between 320 to 500 pixels wide. Your best bet is to target the lowest screen dimensions, so your signature appears at the highest quality on mobiles.

Any text should be large enough to read on a smartphone’s smaller screen.

However, remember that the predominantly landscape shape of an email when read on a desktop conflicts with the portrait layout of a smartphone screen.

For mobile users, we recommend that the email signature dimensions are 320 pixels in width. This is because mobile device screen sizes are typically between 320 to 500 pixels wide. Your best bet is to target the lowest screen dimensions, so your signature appears at the highest quality on mobiles.

Desktop email signature size

For desktop users, the industry-standard image size for email signatures is about 650 pixels in width. However, we recommend using a slightly smaller dimension of 600 pixels wide and between 150 to 200 pixels high.

This will make it a lot easier to create a clean email signature design that won’t have its edges cropped. Most emails will be seen at this size, making it well-suited for the range of email clients such as Outlook and Gmail.

A disadvantage of this method is that the text will extend beyond the edge of the signature when the image is viewed in a window wider than 600 pixels. This will make it appear to be restricted to the bottom left-hand corner.

To overcome this, the image can be placed in an HTML table with complimentary colors so the branding extends to the edge of the message while the image remains the same.

Alternatively, to reduce scaling issues, ensure the maximum email signature size is 450 pixels in width. This provides plenty of space to include all relevant contact information. All required elements of the signature will appear while reducing any scaling issues on mobile devices.

Email signature size dimensions

Elements such as a company logo, social media icons, or banner images are integral to a professional signature design.

The ideal image size for email signatures should be 300 to 400 pixels wide and 70 to 100 pixels high. If the image is a banner, we recommend a maximum height of 100 pixels.

The image should also be optimized for a web resolution of 72dpi, so it displays correctly.

Related guides

• Email signature format

• Email signature fonts

• Company logos in email signatures