Email Size Calculator
This email size calculator works out how big an email is once it's sent. Attachments grow by about a third when they're encoded for sending, so a file under a provider's limit can still be too big. Add your files and see the estimated size, and whether it fits Gmail, Outlook.com, Microsoft 365, Yahoo, iCloud, Proton and Zoho limits.
Add your attachments. See if the email will go through.
100% free • No signup • Runs in your browser
How to use the Email Size Calculator
- 1
Add your attachments
Choose the files you plan to send, or type their sizes. Files are only measured in your browser, never uploaded.
- 2
Paste the body if you like
Add the email text or HTML to include it, and to check whether Gmail will clip a long HTML email.
- 3
Check each provider
See the estimated size once sent, and whether it fits each provider's limit.
Email size limits by provider
From each provider's help pages, September 2026. Some count only the attached files; others count the whole email. Encoding adds about 33% (RFC 2045).
| Provider | Limit | Details |
|---|---|---|
| Gmail | 25 MB | Bigger files are sent as a Google Drive link instead. Source |
| Google Workspace | 25 MB | Counted before encoding. Enterprise Plus allows 50 MB on the web. Source |
| Outlook.com | 25 MB | Text, inserted and attached files all count. OneDrive links don't. Source |
| Microsoft 365 | 35 MB | Default for sending (36 MB to receive); admins can set 1 to 150 MB. Source |
| Yahoo Mail | 25 MB | The total of all attached files, sending or receiving. Source |
| iCloud Mail | 20 MB | Up to 5 GB with Mail Drop turned on. Source |
| Proton Mail | 25 MB | For sending; up to 50 MB when receiving. Source |
| Zoho Mail (personal) | 20 MB | Including all attachments. Source |
Gmail also clips long emails: when the HTML passes about 102 KB, the rest is hidden behind "View entire message". Google doesn't publish this figure; it comes from Litmus and Email on Acid, and images don't count toward it.
Frequently Asked Questions
Why is my email bigger than my attachments?
Attachments are sent in base64 encoding, which RFC 2045 says makes data about 33% larger, plus line breaks. So a 20 MB file travels as about 27 MB, which is over a 25 MB whole-message limit.
What is Gmail's attachment size limit?
25 MB of attachments for personal Gmail. If your files add up to more, Gmail removes them and adds a Google Drive link instead. Google Workspace allows 25 MB, or 50 MB on the web for Enterprise Plus.
What is Outlook's attachment size limit?
Outlook.com allows 25 MB per email, counting the text and all attachments; files shared as OneDrive links don't count. Microsoft 365 work accounts default to 35 MB for sending, and admins can set anywhere from 1 to 150 MB.
Why does Gmail clip my email?
Gmail hides the rest of a message whose HTML code passes about 102 KB, showing "View entire message" instead. Google doesn't publish the figure; it comes from Litmus and Email on Acid, and images don't count toward it.
How do I send a file that's too big?
Share it as a link instead: Google Drive from Gmail, OneDrive from Outlook, or iCloud Mail Drop, which handles attachments up to 5 GB. Compressing into a ZIP helps with documents but rarely with photos or video.
Are my files uploaded?
No. The tool reads only each file's size in your browser. The files themselves never leave your computer.