Split PDF by File Size
Cut a large PDF into parts that each stay under 5, 10, 20 or 25 MB, or into 18 MB parts that fit a 25 MB email limit.
Select a PDF fileor drop it anywhere on this page, or paste
Opens in your browser. Nothing is uploaded.
Split PDF by File Size, free and private
Split a PDF by file size for free. Pick a maximum such as 5 MB, 10 MB or 20 MB, and the tool cuts the PDF into smaller files that each stay under it. Use it when an email or an upload form rejects one large file.
Pages go into the parts as they are, in their original order. Nothing is compressed or turned into an image. The PDF is read in your browser and never uploaded.
How to split a PDF by file size
- 1
Add your PDF
Press Select a PDF file or drop the file onto the page. Under the options, the tool shows the file size and a rough count of the parts to expect.
- 2
Pick the maximum size per part
Choose 5 MB, 10 MB, 20 MB or 25 MB. For Gmail or Yahoo, choose Email, which makes 18 MB parts. For any other limit, press Custom and type a size like 8 MB or 500 KB.
- 3
Split the PDF by size
Press Split by size. The tool fills the first part with as many pages as fit under your limit, then starts the next part with the following page.
- 4
Download the ZIP
Press Download ZIP. The parts are named after your file, such as report-part-1.pdf and report-part-2.pdf, so they sort in page order.
Why use PDFToolz for this
Every part is measured
Pages in one PDF share fonts and images, so ten pages are rarely ten times the size of one. The tool saves each candidate part and checks its real size before it accepts it. The file you download is the file it measured.
Fewest parts in page order
Each part takes the longest run of pages that fits. Pages are never reordered, so part 2 starts on the page after the last page of part 1.
Warns about oversized pages
A page that is bigger than the limit on its own still becomes a part by itself. The result screen names that page and its size, so you know which part to compress.
No upload, no account
There is no sign-up, watermark or page cap. The split runs on your device, so a contract or a medical record stays on it.
How to split a PDF for an email attachment limit
Gmail and Yahoo Mail allow 25 MB of attachments per message. Outlook.com allows 20 MB. Email sends attachments as text, and that encoding makes a file about 37% larger. A 24 MB PDF therefore counts as about 33 MB and bounces.
The Email preset accounts for this. It makes parts of at most 18 MB, which come to about 24.6 MB once encoded, so each part fits a 25 MB limit. For Outlook.com, press Custom and type 14 MB. Send each part in its own email.
How to split a PDF into smaller files for an upload form
Court filing systems and grant portals often cap each upload at 5 MB or 10 MB. Pick that preset, or type the exact limit under Custom. Every part comes out at or below the number you set.
The tool counts 1 MB as 1,048,576 bytes, the way Windows shows file sizes. Some portals count 1 MB as 1,000,000 bytes, which is about 5% less. If a part near the limit is rejected, type a slightly smaller size such as 9.5 MB.
How the tool decides where to cut
The tool cannot add up page sizes, because a font or image used on many pages is stored once per file. So it builds real parts and measures them:
- It starts with a guess from the average page size of your file and saves that many pages as a test part.
- If the test part fits, it doubles the page count until a test part is too big. If the first guess is too big, it tries fewer pages.
- It then halves the gap between the longest part that fits and the shortest that does not, until a single page decides it. A 40-page part takes about 7 test saves.
- The next part starts with the page count of the last one as its guess, so a document with even pages needs few saves per part.
When a single page is over the limit
A page with a large scan or photo can be bigger than the limit by itself. The tool cannot cut a page in half, so that page goes into a part of its own and the result screen marks it.
To shrink that part, open Compress PDF to Size and give it the same limit. It lowers image quality only as far as needed. If most pages are large, compress the whole PDF first and then split it. A PDF with only one page cannot be split at all, so the tool points you to Compress PDF to Size instead.
Split by size, by page count or by ranges
Use this tool when the receiver has a size limit. If you need a fixed number of pages per file, or exact ranges like 1 to 10 and 11 to 30, use Split PDF. To keep only some pages, use Extract PDF Pages. To join the parts again later, use Merge PDF.
What the parts keep and what they drop
Pages are copied, not redrawn, so the page content stays as it was:
- Text stays selectable and searchable. Images keep their full resolution.
- Page sizes, crop boxes and rotation stay the same, so landscape and sideways pages still open the right way up.
- Comments and web links stay on their pages. Links that jump to another page of the PDF stop working.
- Bookmarks and document details such as title and author are not copied. Fillable form fields may stop working, so fill in and flatten a form before you split it.
- If the PDF opens without a password but blocks printing or copying, the parts are saved without those restrictions. Add a password again with Protect PDF if you need one.
Limits
The smallest size you can set is 100 KB. If the PDF is already under your limit, you get the original file back unchanged.
The whole PDF and all of its parts are held in memory while it is split. A file of several hundred MB may be too large for a phone, so use a computer for those. Each part needs a few test saves, so a file with hundreds of pages can take a minute. If the PDF asks for a password to open, remove it first with Unlock PDF.
Frequently asked questions
Add the PDF, pick 5, 10, 20 or 25 MB or type a custom size, and press Split by size. Every part stays under that size, and all parts download in one ZIP. There is no sign-up or watermark.
Pick the Email preset and press Split by size. It makes parts of up to 18 MB, which fit Gmail's and Yahoo's 25 MB limit after email encoding. For Outlook.com's 20 MB limit, use Custom 14 MB. Attach each part to its own email.
Email turns attachments into text before sending, which adds about 37%. A 24 MB file becomes about 33 MB on the way. Keep each file at 18 MB or less for a 25 MB limit.
Yes. Acrobat Pro has a split by file size option, and this tool does the same in your browser at no cost. It works on Windows, Mac, Linux, iPhone and Android in a current browser.
The next page did not fit. A part takes the longest run of pages under the limit, and the page that would push it over starts the next part.
That page becomes a part on its own, and the result screen names it with its size. Run that part through Compress PDF to Size with the same limit to bring it under.
No. Pages are copied without compression, so text and images are unchanged. To make one file smaller instead of cutting it up, use Compress PDF.
No. The PDF is read and split in your browser, and the parts are built on your device.
