Email attachment size limits for Gmail, Outlook, Yahoo, iCloud and more

1. Attachment limits by email service

Limits are per message unless the row says otherwise. "Over the limit" is what the provider says happens, where it says anything.

• A Microsoft figure that looks out of date, but is not. Microsoft's Outlook help gives 10 MB as the default for business (Exchange) accounts. Its Exchange Online limits page lists that as the default for Exchange Server, which an organisation runs on its own servers; Exchange Online, the email in Microsoft 365, defaults to 35 MB. If your employer runs its own Exchange, its IT team sets the figure.
• Not listed: mail.com. Its product page gives free accounts 30 MB and its help centre mentions 50 MB. Both say 100 MB for Premium.
• Providers change these figures without notice. Where a linked page disagrees with this table, the linked page is right.

2. Per-file limits on official upload portals

These portals limit each file rather than the whole submission, and most of their limits are far below email's. They are the ones whose limit an official government page states; if yours is not here, its upload page or help pages are the place to look.

USCIS asks for files without passwords. If a statement arrived password-protected and you are entitled to remove the password, Unlock PDF does it in your browser.

4. Why a file under the limit can still be refused

1. The limit is for the whole message. Gmail counts the "total attachment size", Yahoo "the sum of all attached files". Three 9 MB scans make 27 MB, which is over Gmail's 25 MB although each file is under it.
2. Sending makes the file bigger. Email carries attachments as text, in an encoding called Base64 that turns every 3 bytes into 4 characters, broken into lines of at most 76 characters (RFC 2045). Microsoft puts the growth at 33% and Google at about 37%; Google's figure matches Base64 with its line breaks counted, Microsoft's without. Some limits are measured before the growth (Google's sending limits) and some after (Google's receiving limits, and Microsoft's for mail leaving its data centres). By Google's figure, a 25 MB attachment travels as about 34 MB of email.
3. The recipient's service has a limit too. A message has to fit at both ends. iCloud Mail's 20 MB and Yahoo Mail's 25 MB apply to incoming mail; a Google Workspace Enterprise Standard mailbox accepts 50 MB after encoding, which by Google's 37% is about 36 MB of files.
4. Nobody says what a megabyte is. None of the help pages above says whether it means 1,000,000 bytes or 1,048,576. Computers disagree as well: Apple measures in decimal and notes that some apps and older systems, such as OS X Leopard and earlier, report in binary, and Windows File Explorer reports in binary. So the same PDF shows as 24.5 MB on a Windows PC and 25.7 MB on a Mac: under 25 MB by one count, over it by the other. The checker calls that case borderline rather than guess.

5. How to get a PDF under the limit

Start with what the PDF is made of, because that decides what will work. A PDF exported from a word processor is usually small; when a PDF is big, the size is nearly always in pictures: scans, phone photos, or images placed in the document. A PDF made from phone photos keeps each photo as it was (Images to PDF does not re-encode JPG or PNG), so ten 3 MB photos make a PDF of about 30 MB.

1. Compress it, and let it reduce the pictures. Compress PDF changes no picture by default: it repacks the file and, where every page passes a comparison check, compacts embedded fonts. On a scan that saves little, because the size is in the pictures. Under Pictures, choose Reduce: photos and scans are re-encoded smaller, fine detail softens slightly, and in our tests a phone-photo PDF came out 93% smaller and a scanned page 72% smaller, with text and layout untouched. Smallest goes further, with visible loss; fine for sending, not for keeping. Enter the limit as a target size (1 MB is 1,000,000 bytes there) and the result says whether it was met. It re-encodes ordinary JPEG pictures only, leaves other kinds as they are and says how many, and returns signed PDFs unchanged, because rewriting one would break the signature.
2. If black and white will do, take the colour out. Grayscale PDF converts pictures to single-channel grey, which often makes a colour scan smaller, and rewrites text colour without turning pages into images, so the text stays selectable. It reports the size change either way: a mostly-text PDF barely changes, and a tightly compressed scan can come out larger. Only do this where a black-and-white copy is acceptable.
3. Send only the pages that were asked for. Delete pages or Extract pages builds a new PDF from the pages you keep, so a dropped page's own pictures go with it.
4. Split it into parts that each fit. In Split PDF by size, choose Around a file size and enter the limit. It builds each part and measures it rather than guessing from an average page, and says so if a very long document made it estimate the later cuts. Pages share fonts and pictures, so the parts usually add up to more than the original; a single page bigger than the limit becomes a part of its own, over the target, and the result says so; and links from one part to another stop working. This helps only where the recipient accepts several emails or uploads. For a page limit, such as the IRS's 120 pages per PDF, choose Every N pages instead.
5. Or send a link from your own email service. Gmail's Drive link, OneDrive in Outlook, Mail Drop in iCloud Mail, GMX Cloud, Zoho's Huge Attachments and Proton Drive are in the table above. The file is then stored by the company that already handles your email, rather than a new one. A portal needs the file itself.

Zipping a PDF rarely saves much, because most of a large PDF is pictures that are already compressed, and a portal may not take a ZIP file at all: USCIS, for one, asks for PDF, JPG or JPEG.

Common questions

What is the maximum attachment size in Gmail?

25 MB for a personal Gmail account, counting all the attachments on a message together. If the total is larger, Gmail removes the attachments and puts a Google Drive link in the email instead. Work and school accounts follow their Google Workspace edition: 25 MB to send on Business, Education and Enterprise Standard, and up to 50 MB on Enterprise Plus in Gmail on the web.

What is the attachment size limit in Outlook?

It depends which Outlook. Outlook.com on the web allows 25 MB of attached files, and OneDrive files of up to 2 GB shared as links. Microsoft gives 20 MB, message included, for Outlook.com and Gmail accounts used in the Outlook app. Microsoft 365 work and school mailboxes default to 35 MB to send and 36 MB to receive, and an administrator can set anything from 1 MB to 150 MB.

Why was my email rejected when the attachment was under 25 MB?

Usually for one of three reasons. Attachments are encoded as text for sending, which Microsoft says adds 33% and Google about 37%, and some services measure their limit after that growth. The recipient’s service has its own limit: iCloud Mail’s 20 MB applies to incoming mail too. And the limit covers every attachment on the message together, not each file. Aim well under the limit, or send a link.

How do I make a PDF small enough to email?

If it is made of scans or photos, compress it with picture reduction turned on, because that is where the size is. Converting a colour scan to greyscale often helps too. If it is still too big, send only the pages that are needed, or split it into parts that each fit and send them separately. Otherwise use your provider’s own link option: Google Drive in Gmail, OneDrive in Outlook, Mail Drop in iCloud Mail.

Does the file checker on this page upload my file?

No. It reads two things the browser already knows about a file you choose, its name and its size, and compares the size with the limits on this page. It does not open the file or read what is in it, sends nothing anywhere and saves nothing; reloading the page clears it.