Email Attachment Size Limits and How to Make Your Files Fit
Personal Gmail accounts can send attachments up to 25 MB in total per email, and most other providers set similar limits of around 20–25 MB. Because email encoding makes files about a third larger in transit, a file just under the limit can still be rejected. To make files fit, shrink photos to 100–300 KB each, combine scans into one smaller PDF, or share large files as a cloud link.
Attachment limits by provider
| Provider | Limit per email | Notes |
|---|---|---|
| Gmail (personal) | 25 MB | Workspace accounts: set by the administrator |
| Outlook / Microsoft 365 | About 20–25 MB | Varies by account type and app; check Microsoft's help pages |
| Other providers | Often 10–25 MB | The receiver's limit can be lower than yours |
The limit applies to the whole message: all attachments together, plus the text and any pictures pasted into the email body.
Why files grow when you send them
Email was designed for text, so attachments are converted with an encoding called Base64, which turns every 3 bytes into 4 characters. That makes each file about 33% larger on the way. A 20 MB attachment becomes roughly 27 MB in transit, which can exceed a 25 MB limit. Aim to keep attachments to about three quarters of the limit.
How to make photos fit
Phone photos are usually 2–5 MB each because they are made for printing and zooming. For someone viewing them on a screen, 100–300 KB is plenty.
- Open the image resizer and add one photo at a time.
- Set a target of 200–300 KB for photos, or 100 KB for screenshots and simple images.
- Download and attach the smaller files.
Ten photos at 4 MB each (40 MB) become about 2–3 MB in total, well inside any limit.
How to make documents fit
- Several scanned pages: resize each page photo to 100–200 KB, then combine them into one PDF with JPG to PDF. A five-page document ends up around 1 MB.
- Several PDFs: join them into one file with Merge PDF so the recipient gets a single, ordered attachment.
- Very large files (videos, big presentations): upload them to Google Drive, OneDrive or Dropbox and send a link instead.
Checklist before you press send
- Total attachment size is comfortably below the limit (about 75% of it).
- Photos are resized to a sensible size for screens.
- Multi-page documents are combined into one clearly named PDF.
- For anything over the limit, you have shared a link and checked the sharing permission.
Sources
- Gmail Help – Attachment size limits (checked October 2026)
Frequently asked questions
What is Gmail's attachment size limit?
For personal Gmail accounts the limit is 25 MB. For work and school accounts, the Google Workspace administrator sets the limit.
Why does my email bounce when the file is under 25 MB?
Attachments are encoded as text for sending, which makes them roughly 33% larger. The recipient's mail server may also have a lower limit than yours.
What is the Outlook attachment limit?
It depends on the account type and the Outlook app; published figures are usually 20 or 25 MB. Check your own provider's help page, and keep a margin below the limit.
How do I send files larger than the limit?
Shrink them first, or upload them to a cloud service such as Google Drive or OneDrive and send a link. Gmail offers to add a Drive link automatically for files that are too large.
How small should photos be for email?
For viewing on screen, 100–300 KB per photo is plenty. A phone photo is often 2–5 MB, so resizing ten photos can take an email from 30 MB to under 3 MB.