Email attachment limits are not what they say on the tin. Here is the real number for each provider, how many scanned pages actually fit under it, and a compressor that gets you there without destroying your text.
Quick answer: Gmail's 25 MB limit is really about 18 MB of file — attachments are base64-encoded before sending, which inflates them by roughly a third, and the limit applies to the encoded message. Target 18 MB for Gmail, 15 MB for Outlook, and 5 MB if you are emailing a work address and do not know their limit. Your text stays selectable, and nothing is uploaded anywhere.
Compress a PDF to fit your email Nothing uploaded · text stays selectable · no watermark
This catches people out constantly, and almost nothing explains it. Email cannot carry raw binary data, so every attachment is base64-encoded before it is sent — three bytes of file become four characters on the wire, plus line breaks. That is an increase of roughly a third.
Providers apply their limit to the encoded message, not to the file sitting on your disk. So Gmail's widely-quoted 25 MB is about 18 MB of actual file, and a 20 MB cap is nearer 15 MB. A 22 MB PDF that "should" fit inside 25 MB will be rejected, and the error message rarely explains why.
Aim at the real number rather than the advertised one. The button above targets 18 MB for exactly this reason.
What the limits actually are
Checked 2026-09-04 against the providers' own documentation. Worth re-checking before you rely on them — these change, and most guides online are quoting figures from years ago.
Provider
Stated limit
Real file size
Gmail
25 MB
~18 MB
Outlook.com
20 MB
~15 MB
Corporate Exchange
often 10 MB
~7.5 MB
Corporate mail servers are the strictest and the least predictable — a 10 MB cap is common and some finance and government systems sit at 5 MB. If you are sending to a work address and do not know the limit, targeting 5 MB is the safe move; it costs you very little on a scanned document.
How many scanned pages fit in one email
Measured with this site's own engine on a real 200 dpi colour scan — a page of body text, a photograph and paper grain. The middle column is what most people would consider a normal-looking scan on screen.
Limit
Sharp — 2200 px
Readable — 1325 px
Small — 450 px
Gmail — 25 MB stated
54
172
1307
Gmail — ~18 MB real
39
124
941
Outlook.com — 20 MB
43
138
1046
~15 MB real (20 MB cap)
32
103
784
A cautious 10 MB
21
69
523
A strict 5 MB
10
34
261
Turning on grayscale takes roughly another 6% off a colour document. On a scan that was black ink on white paper to begin with, that is free — there was no colour information worth keeping.
If it still will not fit
In the order actually worth trying:
Grayscale first. It is the cheapest real saving and usually invisible on a document scan.
Send fewer pages.Split PDF lets you pull out just the pages the recipient needs. Halving the page count halves the file — no compression setting comes close.
Share a link. Above roughly 20 MB this is what the recipient would rather have anyway, and it survives forwarding.
Do not zip it. A PDF full of JPEG images is already compressed; putting it in a ZIP typically saves one or two percent and adds a step for the recipient.
One thing to avoid: tools that "compress" by rendering every page to a picture. On a scan that saves marginally more than doing it properly and costs you the searchable text layer. On a text document it makes the file larger — we measured a ten-page text PDF coming back thirteen times its original size that way.
Compress a PDF for email in three steps
1
Open with 18 MB set
Or pick 5 MB if you are emailing a work address and do not know their limit.
2
Drop your PDF in
Read in your browser, never uploaded. You are told what the file is made of before anything happens to it.
3
Compress and attach
Text stays selectable, so the recipient can still search and copy from it.
Frequently Asked Questions
Less than the number your provider advertises. Attachments are base64-encoded before sending, which inflates them by about a third, and the limit applies to the encoded message rather than to the file on your disk. Gmail's 25 MB is therefore roughly 18 MB of actual file, and a 20 MB cap is nearer 15 MB. Corporate mail servers are often stricter still, commonly 10 MB and sometimes 5 MB.
Because base64 encoding turned it into about 29 MB on the wire. Email cannot carry raw binary, so every attachment is re-encoded before it is sent — three bytes become four characters — and Gmail measures the encoded message. Compress the PDF to about 18 MB and it will go through.
Measured on a real 200 dpi colour scan with our own engine: under Gmail's real 18 MB limit, roughly 39 pages at a sharp 2200 px, 124 pages at a readable 1325 px, or several hundred at a small 450 px. Under a strict 5 MB corporate limit that becomes about 10, 34 and 256 pages respectively. Plain text pages cost far less; photo-heavy pages cost more.
Not with the method this tool uses by default. It re-encodes the embedded pictures and leaves text, fonts, vector graphics, hyperlinks, bookmarks and form fields exactly as they were, so the recipient can still search, select and copy. A scanned document with an OCR layer keeps that layer as well.
Usually not. A PDF containing JPEG images is already compressed, so a ZIP typically saves one or two percent while adding a step for the recipient and, on some corporate mail systems, triggering a filter that blocks the attachment entirely. Compressing the PDF itself is both more effective and less trouble.
Try grayscale first — it takes roughly another 5 percent off a colour document and is usually invisible on a document scan. Then send fewer pages: Split PDF lets you pull out only the ones the recipient needs, and halving the page count halves the file, which no compression setting can match. Above about 20 MB, sharing a link is what most recipients would prefer anyway.