Why convert BMP to JPG
A BMP stores pixels more or less raw, which is why a modest image can occupy tens of megabytes. The format survives mostly in older Windows software, scientific instruments and scanner output. Almost nothing is lost by moving to JPEG, because the enormous size buys precision that photographs do not need, and the resulting file is vastly easier to email, upload or store.
What this conversion costs you
- Lossy compression is introduced. BMP is uncompressed, so this is the first time the image is approximated at all. At high quality the difference is essentially invisible for photographs.
- Sharp edges may soften slightly. If the BMP is a diagram or contains text, JPEG's smoothing can blur hard edges. PNG is the better destination for that kind of image.
When not to do this
Do not use JPG for scanned text, engineering drawings or screenshots where legibility matters — convert those to PNG, which is still dramatically smaller than BMP and keeps edges crisp.
Common questions
Why are BMP files so enormous?
BMP stores pixel data essentially uncompressed, so file size scales directly with dimensions. A 4000 by 3000 image needs roughly 36 MB regardless of what it depicts.
Does converting BMP to JPG lose quality?
Some, since JPEG is lossy and BMP is not. For photographs at high quality the loss is imperceptible while the size saving is enormous.
Should I convert scanned documents to JPG?
Prefer PNG for scanned text and line drawings. JPEG smoothing blurs the hard edges that make text readable, while PNG keeps them sharp and is still far smaller than BMP.