Mailchimp Email Size Limit: The 102KB Gmail Line Explained

The numbers in one table

There isn't one single cap here, there are a handful of limits that people tend to mix up. The one that bites is the 102KB line, and that's Gmail's rule rather than a hard stop inside Mailchimp. Your campaign will still go out above it. It just won't arrive whole for anyone reading in Gmail.

Item	Limit	Applies to
Message size before Gmail clips	102KB	Message code (HTML, links, tracking) in Gmail
Image file size	1MB maximum (recommended)	Images in templates and campaigns
Template width, new builder	660px	New email builder templates
Template width, legacy builder	600px	Legacy email templates
Recommended image width	660 to 1320 pixels (new builder), 600 to 1200 pixels (legacy)	Email images
Bytes per character	About 1 to 2 bytes	Characters in the email code

All six rows come from Mailchimp's own help pages: the clipping article for the size and byte rows, and the image requirements article for the file size and width rows.

What happens when your campaign goes over 102KB

Gmail shows the top part of the message and then stops. Underneath, your reader sees a View entire message link. Some people click it. Most won't, so anything below the cut, which is often your main call to action, your footer and your unsubscribe details, simply goes unseen.

There's a second problem that's easy to miss. The code Mailchimp uses to track opens sits in the part of the email that gets clipped. So when Gmail trims the message, the open often isn't recorded. That's why Mailchimp recommends keeping emails smaller than 102KB, and it's why a heavy newsletter can look as if it's performing worse than it really is.

Why resizing a picture won't shrink your email

Here's the bit that trips most people up. The size that counts is the underlying code, not the visible words or how big the images look on screen. Mailchimp's help article on Gmail clipping explains that images load from Mailchimp's servers, so changing their dimensions doesn't change the amount of data in the message at all.

What does count is everything written into the HTML: your text, every link URL along with its tracking code, and the styling. Each character is roughly 1 to 2 bytes. Tracked links add bulk quickly, so a long email packed with buttons and links can cross the line even when it has very little copy. Deleting an image does help, because it removes that image's code from the message.

How to check your size and trim it

1. Send the campaign to a test address.
2. Save the source code of that email to a document.
3. Look at that file's size. If it's over 102KB, Gmail will clip it.
4. If you pasted copy in from Word or a web page, run the Clear Styles tool to strip the hidden formatting code that comes with it.
5. Cut images, blocks or links you don't need. Removing an image removes its code.
6. If nothing more can go, swap long sections for Read More links that send people to the full content.

Read More links are the honest fallback for long newsletters. The reader still gets everything, the email stays under the line and your opens stay tracked. If you want ideas for lighter layouts, my comparison of MailerLite and Mailchimp for small senders is a good next stop.

A false alarm from your own test sends

If you send yourself several test emails with the same subject line, Gmail can thread them into a single item and clip that. It looks as if your campaign is too big when it isn't. Change the subject line between tests, or delete the earlier ones, and Mailchimp says clipping shouldn't happen when the real send goes to your contacts.

Image rules worth knowing

Images live under their own guidance. Mailchimp recommends a maximum file size of 1MB per image. Legacy templates are 600 pixels wide and templates in the new builder are 660px wide, with recommended image widths of 660 to 1320 pixels in the new builder and 600 to 1200 pixels in the legacy one. Going wider gives you a sharp image on high resolution screens without changing the clipping maths.

If you're weighing up another email tool

HubSpot's email editor shows an estimated size and compares it against Gmail's 102 KB clipping threshold as you build, though that estimate leaves out content inside personalisation tokens. If a live size warning matters to you, my guide to email marketing software for small businesses covers the wider field.

My advice if you send long newsletters

Write to the 102KB line, not to the look of the email. Check the source file size on every big send, clear pasted styles out of habit, and use Read More links rather than cramming everything in. You'll keep your call to action visible and your open numbers honest. If you're still deciding where to send from, how Constant Contact compares with Mailchimp is worth a read too.

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Frequently asked questions

What is the Mailchimp email size limit?

Mailchimp advises keeping emails under 102KB, the point where Gmail starts clipping. It's a Gmail display rule rather than a block on sending.

What happens when Gmail clips my email?

The rest of the content is hidden behind a View entire message link, and the open tracking code gets cut off too.

Does shrinking an image fix it?

No. Changing image dimensions doesn't change the amount of data, because images load from Mailchimp's servers. Deleting an image does reduce the size.

How big can images be?

Mailchimp recommends a maximum of 1MB per image file.

How do I check my email size?

Send it to a test address, save the source code to a document and look at the file size.