Email Weight

One aspect of deliverability that is often overlooked is the email file size. The size of your email plays a significant role in whether your message makes it to the inbox and how it looks once it gets there.

Overview

Email weight refers to the total file size of an email—typically measured in kilobytes (KB). It affects load time, deliverability, and rendering across devices and email clients. Keeping email weight light is essential for ensuring a smooth, reliable experience for all recipients.

The chart below shows a rough guide to predicting approximate size of an average email by adding together the sizes of common elements. Total email file size recommendation is 1.5 MB including images.

ModuleSize in KB
HTML <head> and <body> only (empty shell)12kb
Preheader3kb
Brand Panel9kb (average)
Hero Banner7kb (average)
Image Modules8kb (average)
Text Modules7kb (average)
Footer Cross-sell Icons15kb
Footer Nav Bar5kb
Ts and Cs10kb (approx average)
Why?

If it takes a long time to download your email, you’ll have lost half your audience who will have become bored and already hit the DELETE button.

Email Clipping

Gmail

Gmail ‘clips’ emails that have a message size >102KB (just the code – not the images as these load separately). The full content is put behind a ‘View entire message’ link. It can also clip the tracking code that measures your open rate. So, to avoid slow loading or clipping, ask your agency to keep the HTML file of your message smaller than 102KB.

Apple Mail

As of iOS 18, Apple Mail clips longer emails by truncating their content, requiring recipients to click “See More” to view the full message. This appears to happen when an email exceeds about 200-350px in length depending on device. This increases the need to optimize email design by keeping messages concise, reducing unnecessary elements and front-loading important content above the fold.

Questions?

Connect with the DLS Team on Slack or by email.

Resources

Check out additional resources.