Email Attachment Size Limits, and How to Get Under Them

The limits, provider by provider

These are the figures each provider publishes. "Send" is what the service lets you attach; "receive" is what it accepts from outside, where the provider states it. A business account on Google Workspace or Microsoft 365 can have different limits set by its administrator.

Provider	Send	Receive	For bigger files
Gmail, personal account	25 MB	Workspace: 50 MB after encoding (Enterprise Standard)	Google Drive link, added automatically above the limit
Outlook.com	25 MB per file	not stated	OneDrive share, up to 2 GB
Microsoft 365 / Exchange Online	35 MB default, admin can set 1 to 150 MB	36 MB default; 112 MB max from outside	OneDrive attachment, up to 2 GB
Yahoo Mail	25 MB, all attachments together	25 MB, all attachments together	not stated
iCloud Mail	20 MB	20 MB	Mail Drop, up to 5 GB, 30 days
Proton Mail	25 MB, up to 100 files	50 MB	not stated

Microsoft's documentation adds a detail the others leave implicit. Exchange Online allows messages of up to 150 MB between users inside Microsoft's data centres, but messages routed outside are subject to a 33 percent encoding increase, so the maximum there is 112 MB, and Outlook on the web restricts what you can send to 25 percent less than the configured limit to leave room for it. Proton says the same in one line: the encoding process makes attached files a bit larger than they are on your computer. That encoding is the reason for the next section.

Why a 20 MB file can fail on a 25 MB limit

Email was built for text. To carry a PDF or a photo, the mail program converts the file's bytes into text with base64, defined in RFC 2045, the MIME standard: every group of 3 bytes becomes 4 characters, and the result is written in lines of no more than 76 characters, each ending in a line break. The file therefore grows on the wire:

Size of an attachment inside the message

encoded ≈ file size × 4 ÷ 3 × 78 ÷ 76 ≈ file size × 1.368

Google quotes the increase as about 37 percent, Microsoft rounds it to 33 percent; the table uses the exact factor from the standard. Dividing a limit by it gives the largest file that fits, and dividing again by the number of files gives a target per file when you are sending several.

Message limit	Largest single file	2 files, each	3 files, each	5 files, each	10 files, each
20 MB	14.6 MB	7.3 MB	4.9 MB	2.9 MB	1.5 MB
25 MB	18.3 MB	9.1 MB	6.1 MB	3.7 MB	1.8 MB
35 MB	25.6 MB	12.8 MB	8.5 MB	5.1 MB	2.6 MB
50 MB	36.5 MB	18.3 MB	12.2 MB	7.3 MB	3.7 MB

So on a 25 MB service the files should add up to about 18.3 MB, and on iCloud's 20 MB to about 14.6 MB. The message text, the signature and any inline images come out of the same budget, so aim a little lower still.

Getting a file under the limit

PDFs

Most of a large PDF is pictures: scans, photos, embedded images at print resolution. The PDF compressor re-encodes those images at a lower resolution and quality while leaving the text sharp, and its target-size option aims straight at a number of megabytes. If the document is long, the PDF splitter cuts it into parts or pulls out just the pages the recipient needs, and each part goes in its own message. For a single page as a picture, PDF to JPG turns it into an image you can compress like a photo.

Photos

A phone photo straight from the camera is several megabytes, and ten of them break every limit in the table. The compress image to target size tool takes a size such as 2 MB or 500 KB and finds the highest quality that stays under it, one photo at a time, so a batch lands at a known total. The image compressor does the same with a quality slider and converts PNG screenshots to JPG or WebP, which are far smaller for photographs. Resizing to the pixels a screen can show, 1,920 wide is plenty for viewing, often removes more than the quality setting does.

Video and everything else

Video is almost never going to fit as an attachment; a minute of phone footage is larger than any limit above. The video compressor brings a short clip down to a target size for a message, and for anything longer a link is the only practical route.

Send a link instead

Every provider in the table offers one. Gmail swaps oversize attachments for a Google Drive link on its own. Outlook.com and Microsoft 365 attach a OneDrive file of up to 2 GB in place of the file. Apple's Mail Drop sends attachments of up to 5 GB through iCloud; the recipient has 30 days to download them and they do not count against your iCloud storage. The recipient does not need an account with the service to download a shared file, and a link cannot bounce for being too large.

Before you press send

Add up the files, multiply by 1.37, and compare with the smaller of your limit and the recipient's. When in doubt, stay under about 14 MB of files.
Compress, then split. A smaller PDF or photo is better for the recipient than three messages; split only when compression is not enough.
Do not zip compressed files. Photos, PDFs and video barely shrink in an archive, and some mail filters block archives.
Above 20 MB, link. A Drive, OneDrive or Mail Drop link works at any size and does not depend on the other side's limit.

Frequently asked questions

What is the maximum attachment size for Gmail?

Google states that for personal Gmail accounts the limit is 25 MB. If your attachments add up to more, Gmail removes them from the message and adds a Google Drive link instead. Work and school accounts get their limits from the Google Workspace administrator; Google's Workspace documentation gives 50 MB for a received message on Enterprise Standard, measured after encoding, which it says adds about 37 percent.

Why does a 20 MB file fail on a 25 MB limit?

Because the file does not travel as 20 MB. Email transports binary files in base64, which the MIME standard defines as 4 characters for every 3 bytes, in lines of at most 76 characters. That makes an attachment about 37 percent larger on the wire, so a 20 MB file becomes roughly 27 MB of message. Microsoft documents the same effect: messages leaving its data centres are subject to a 33 percent encoding increase, and Outlook on the web holds back 25 percent of the configured limit for it. As a rule of thumb, the files you attach should add up to about 70 percent of the stated limit.

How do I send a file that is too big to attach?

The providers all point the same way: share it as a link. Gmail switches to a Google Drive link automatically, Outlook.com and Microsoft 365 offer OneDrive attachments of up to 2 GB, and iCloud Mail offers Mail Drop for attachments up to 5 GB that the recipient can download for 30 days. If you would rather keep it as an attachment, shrink it: compress the PDF, split it into parts, or compress the photos to a size you choose.

Does zipping a PDF or a photo make it smaller?

Rarely by much. JPEG photos, most PDFs and video are already compressed, and a zip archive cannot squeeze them again; it mostly helps with text, spreadsheets and uncompressed images. To get a PDF or a photo under a limit, recompress its images at a lower quality or resolution instead, which is what a PDF compressor or an image compressor does.

Which limit counts, mine or the recipient's?

Both. Your provider checks the message when you send it and the recipient's provider checks it when it arrives, so the smaller of the two decides. Apple notes that a recipient's email app might have a smaller message size limit than Mail Drop allows, and Microsoft notes that some email clients limit individual attachments below the server's message limit. If you do not know the other side's limit, 20 MB of message, about 14 MB of files, is under every figure in the table.

Sources

Written by Tobias Kurth, designer. Updated October 20, 2026.