Email size checker
Measure your email's HTML and see how close it is to the size where Gmail clips it.
Email size checker, the tool
Size
0.0 KB
0 bytes. The reported line is 102 KB, 104,448 bytes.
Paste HTML to measure it.
What is using the space
- Inline styles
- 0 bytes
- Style blocks
- 0 bytes
- Link addresses
- 0 characters in 0 links
- Images
- 0 in all, 0 linked, 0 embedded
- Embedded image data
- 0 characters
- Outlook conditional blocks
- 0
- VML rounded rectangles
- 0
A kilobyte here is 1,024 bytes. The message is called close from 81,920 bytes and flagged from 100,000.
What counts toward Gmail’s 102 KB limit
- What Google says
- Nothing. Google’s Gmail CSS page gives no size limit and does not mention clipping, and a 2018 thread on the email-bugs project found no Google source for 102 KB. It is an observed threshold.
- HTML and CSS
- The limit is on the code. Litmus says it does not include images, and Klaviyo that it covers all text, styling, links and other HTML.
- Link addresses and tracking code
- Mailchimp counts link URLs and tracking code. The checker above shows how many characters sit inside link addresses.
- Images
- The file loaded from elsewhere does not count. An image embedded as base64 is part of the HTML, and base64 is roughly a third larger than the file: a 30,000-byte photo becomes 40,000 characters.
- Markup your platform adds
- Litmus notes that some platforms add markup when they send, so measure the HTML your platform sends.
- What gets cut
- The end of the message: usually the footer, with the unsubscribe link Google wants visible in the body of bulk senders’ marketing mail. Mailchimp says the open-tracking code goes too, so opens can go unrecorded.
- What a kilobyte is
- Tools disagree on 1,000 or 1,024 bytes. This checker counts 1,024, which puts the line at 104,448 bytes. It marks a message from 100,000 bytes, short of 102 KB on either count, and calls it close from 81,920 bytes (80 KB), the ceiling we recommend.
- Where the reports disagree
- Klaviyo lists about 20 KB on iOS and 75 KB on other phones, without saying how it measured. Commenters on the email-bugs thread saw messages clipped just under 100 KB, and others well above it that were not. Hence the margin.
Worked examples
Two ways an email gets heavy, measured on made-up HTML with the same function the checker uses, and drawn to scale against Gmail’s line.
| Example and version | Bytes | Of the line |
|---|---|---|
| The same style on 200 table cellsWritten inline on every cell | 27,307 | |
| The same style on 200 table cellsOnce, in a style block | 7,029 | |
| One 30,000-byte photoEmbedded as base64 | 40,054 | |
| One 30,000-byte photoLinked from a web address | 59 |
Sample The HTML is generated by this page; the scale runs to 120 KB. Moving the style into a block saves 20,278 bytes, and linking the photo saves 39,995. Read Google’s Gmail CSS page before moving rules, and keep layout-critical styles inline.
More free tools
- Email contrast checkerCheck the contrast ratio of a text color on a background against WCAG 2.2 AA and AAA.
- Subject line testerCount a subject line's characters and see how much of it each of five inbox clients shows.
- Spam word checkerFlag the promotional phrases in your copy so you can reread them before you send.
Further reading
Last verified . The sources named on this page were read that day.