TL;DR: Upload your file, click BMP, and download the result — free, browser-based, no sign-up, no watermarks. Files are processed and discarded immediately.
Convert BMP to PDF online for free — turn legacy Windows BMP bitmap images into a portable PDF document with custom page sizing. No sign-up.
BMP to PDF is part of PrivaTools — a free, open-source alternative to iLovePDF, Smallpdf, and Adobe. Server-side tools process your file in an isolated container and discard it immediately; many tools never upload at all and run entirely in your browser.
BMP is uncompressed; PDF stores images in DCT (JPEG) or Flate format. A 5 MB BMP usually becomes a few hundred KB inside the PDF.
By default the conversion is near-lossless using high-quality JPEG. For 100% lossless, convert via PNG first (PNG-to-PDF) — slightly larger output.
Up to the 500 MB total file limit. Several dozen images is routine.
See how PrivaTools compares to iLovePDF, Smallpdf, Adobe Acrobat, and other free PDF tools.