Drop your BMP files into the emerald zone below to create a PDF document. A bitmap stores every pixel uncompressed, so one A4 page scanned at 300 dpi occupies about 26 MB on disk, and repacking it losslessly into a document typically cuts that by 80 to 95 percent with identical pixel values. We avoid JPEG deliberately, because it blurs scanned text and puts halos along line work. The processing runs on your CPU and your files are never uploaded.
Your files are read by JavaScript running on your own machine. There is no upload, no queue, and no copy on our server to delete later.
Drag a card to reorder it, or use the arrows under each card. The order here is the order in the output. Each card is a preview of the finished page, so what you see is what the PDF will contain.
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Starting
This is your processor doing the work, so the time it takes depends on your machine and not on how many other people are on the site.
The converter above is live and ready for bitmaps. The notes below explain why your source bitmaps are so enormous and why most conversion engines damage them - the arithmetic behind a 26 MB scan, what a photographic filter does to technical line art, and how a lossless rewrite gets you the size reduction without the collateral damage.
Two minutes. Nothing to install, and no account for your first run. This free pdf converter runs as JavaScript inside the page you are reading, so every step relies on your own hardware.
Click the drop zone above, or drag your bitmaps onto the page. The script reads the bitmap info header as each file lands, reporting the true pixel dimensions, the color depth and whatever resolution the scanner wrote in. Nothing is estimated. Those values come from the header, not from a guess based on file size.
Card order is page order. Drag the cards until the sequence matches the paperwork. The A to Z sort reads embedded numbers as numbers, so scan 2 lands before scan 10 rather than after it, which matters when you are working through several hundred sequentially named files.
For scanned paperwork, choose A4 or US Letter to place the graphics on standard sheets. If you are reproducing industrial or medical imagery at an exact physical scale, choose Fit to image and set Assumed resolution to match your scanner, which is usually 300 dpi.
Press Convert to PDF. The processing happens on your local machine. Compare the finished pdf file against your original bitmaps: an 80 to 95 percent reduction is normal, and it costs you nothing in visual fidelity.
BMP is the simplest raster format still in common use, and the file sizes follow directly from that simplicity. The structure stores one entry per pixel and applies no compression at all. Nothing clever happens anywhere in the format. That is exactly why it survives in industrial settings, where a clever file format is a liability rather than a feature.
The math is rigid. A 24-bit bitmap needs three bytes per pixel, with every row padded out to a four-byte boundary, so an A4 page scanned at 300 dpi comes to 2480 by 3508 pixels and occupies roughly 26 megabytes. Every page costs that. A twenty page contract reaches half a gigabyte before you have even tried to attach it to anything.
| Source Content | Pixel Dimensions | BMP Size (24-bit) |
|---|---|---|
| A4 scanned at 150 dpi | 1240 x 1754 | About 6.5 MB |
| A4 scanned at 300 dpi | 2480 x 3508 | About 26 MB |
| A4 scanned at 600 dpi | 4960 x 7016 | About 104 MB |
| Full HD screen capture | 1920 x 1080 | About 6.2 MB |
The waste is particularly annoying with scanned documents, because they are extremely compressible. A page of text is mostly white space, and long runs of identical pixels are the easiest thing in the world for a compressor to collapse. The bitmap format simply declines to try.
The tool reads the bitmap info header rather than inferring dimensions from the byte count. Two fields there matter. The height is a signed value, so a negative height means the rows are stored top to bottom instead of the bottom-up order the format defaults to. Software that reads that field as unsigned reports a height of about four billion pixels and falls over.
The second field is resolution, stored as pixels per meter. When your scanner fills it in correctly, the tool converts it to dpi and can build the page at the exact physical size of the original document. Plenty of cheap firmware leaves it at zero. When that happens there is no honest way to know how large the image was meant to print, and the interface says so rather than inventing a number.
The PDF specification has no filter that accepts raw uncompressed bitmap data, so a BMP has to be decoded and repacked into a format the container supports. That single decision defines how good the tool is, and most converters get it wrong by defaulting to JPEG.
Consider what a BMP usually contains. It is scanner output, a screen capture, or a frame from an industrial machine vision camera, which means the material is dominated by text, line work, flat color and hard boundaries. It is also completely uncompressed, so it has never been through a single generation of loss.
Running that through a JPEG filter destroys it. Ringing halos appear around every character of scanned text, mosquito noise settles along the line work, and flat areas of exact color break up into uneven blocks. The damage is permanent, and it is inflicted to save space that a lossless compressor recovers anyway.
So the engine rewrites your bitmap as a lossless PNG and embeds it with FlateDecode. Deflate is very effective on this kind of data. Long runs of identical pixels collapse almost perfectly, and the finished document is typically 80 to 95 percent lighter than the source files with every pixel value unchanged.
| Conversion Route | Data Loss | Scanned Text | 26 MB Scan Becomes |
|---|---|---|---|
| Repacked as PNG (CartHacker) | None. Pixel identical. | Matches the original exactly. | Typically 1 to 4 MB |
| Forced through JPEG (typical) | Permanent. | Ringing halos on every character. | Typically 1 to 3 MB |
Look at the last column. Running a photographic filter over a flat document scan saves you almost nothing on file size and charges you permanent visual damage for it. On a contract where a signature or a handwritten annotation has to stay legible, that is not a trade worth making.
On volume: the free engine handles ordinary batches without trouble. Anonymous visitors get one operation every 12 hours and a free CartHacker account raises that to two, with both capped at 20 files or 100 MB per batch. Uncompressed bitmaps hit that 100 MB ceiling fast, often after three or four high resolution scans. CartHacker Premium removes the operation counter and raises the ceiling to 100 files and 500 MB.
Check the interface card. When it reads BMP repacked losslessly as PNG, that is a description of what happened to your file. Zoom the finished PDF to 100 percent on a line of scanned text and compare it against the source: they are indistinguishable, because the pixel data is identical.
BMP looks like a relic until you find out where it comes from. The format persists in environments where predictability outranks storage efficiency, and in those settings uncompressed output is a deliberate requirement.
The BMP format is old and narrowly defined, so it carries virtually no metadata. No EXIF blocks. No GPS coordinates, no camera serial numbers, no editing history. A bitmap is an array of pixels behind a short header. Next to a smartphone photograph, which leaks device and location data by default, a BMP is close to anonymous.
Data security matters more than usual with bitmaps, because of what they typically hold. Unredacted contracts, internal system captures and medical records are not files to hand to an unknown cloud server just to make them smaller.
This tool has no upload phase. The JavaScript engine uses the HTML5 File API to read your uncompressed graphics into local memory. The conversion runs on your own CPU and the document is assembled in your browser, so no external server ever ingests, processes or keeps a copy.
There is a speed argument too. Uploading half a gigabyte of raw 300 dpi scans takes minutes and saturates your connection. Processing the same batch locally takes seconds, because the data never goes anywhere.
The 30 second offline test. Open this page, turn off your Wi-Fi, drop in a heavy bitmap and press convert. A cloud tool fails on the spot. This one does the arithmetic and hands you the PDF.
The only packet that reaches our infrastructure is an anonymous timestamp enforcing the free tier limits. It records that an operation happened. It never receives your file data, your file names or your directory structure.
No. A PDF cannot carry raw bitmap data, so the engine decodes the image and rewrites it as a lossless PNG rather than a lossy JPEG. Every pixel value in the new document is identical to the one in your source file. You get a large reduction in file size with no compression artifacts and no blurred text.
BMP applies no compression whatsoever. A 24-bit bitmap allocates three bytes to every pixel, with each row padded out to a four-byte boundary. An A4 page scanned at 300 dpi therefore takes about 26 megabytes, whether the page is covered in dense text or completely blank.
Drop your batch of BMP files into the drop zone and leave the Merge all images into one PDF option active. Drag the cards to sequence the pages. The script compiles all of the graphics into a single multi-page document in the order you set.
For scanned documents and interface captures, expect a reduction of 80 to 95 percent. Deflate compression is extremely efficient at collapsing the long runs of identical white pixels that make up most of a scanned page. Photographic content compresses less well, because it has fewer exact repetitions to exploit.
Because JPEG is built for continuous-tone photography. Pushing line art, flat color or scanned text through it introduces permanent ringing halos and mosquito noise. On flat document scans a lossless PNG repack often produces a smaller file anyway, which makes JPEG both destructive and pointless here.
Yes. The converter uses a zero-trust local architecture: the JavaScript engine runs the conversion on your own CPU and the code contains no endpoint that could upload your bitmaps anywhere. Your data stays on your hardware from start to finish.
Choose A4 or US Letter to place the graphics on standard printer paper. If you are handling architectural drafts or medical imagery that needs exact physical scaling, choose Fit to image and enter the resolution your scanner used, usually 300 dpi.
Yes. The interface gives every card explicit sequence buttons rather than relying on mobile drag-and-drop. Be careful with batch sizes, though: uncompressed bitmaps need a lot of memory, and an older phone will hit its ceiling well before a laptop does.
Yes. The browser decoder handles the common BMP color depths, from 1-bit black and white through to 32-bit color. Low-depth monochrome files convert very quickly and produce the largest size reductions of all, because a bilevel scan is almost entirely long runs of a single value.
There are no uploads at all, but there are batch limits. Anonymous visitors get one operation every 12 hours and free accounts get two, with both capped at 20 files or 100 MB. Uncompressed bitmaps reach that 100 MB ceiling after three or four high resolution scans, so Premium raises it to 100 files and 500 MB.
No. There is no forced branding, trial stamp or hidden attribution link in the output. The resulting PDF holds your scans and nothing else, ready for corporate or commercial distribution as it is.
All of these run the same way: your file is read by JavaScript on your own machine, the work happens on your processor, and the result is handed back to you as a download that never existed anywhere else.
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Change the link after printing and count the scans. 5 tracked codes on a free account, static codes unlimited.
Anonymous visitors get one operation per 12 hours, per network address. That is not a sales tactic, it is the only lever we have: this tool runs on your processor, not ours, so the run itself earns us nothing. An account tells us who you are, and the ceiling goes up the moment you have one. Your allowance resets in 12 h.
No credit card, no trial period, no sales call. Join with Google, GitHub, Facebook or email.
Free accounts get two operations per 12 hours, and yours reset in 12 h. Waiting costs you nothing and is a completely reasonable choice. If PDF work is a weekly job rather than a one-off, the counter is the wrong tool for you and Premium takes it off the page.
Cancel anytime. Everything you have already produced stays yours either way.