ALL IMAGE TOOLS56
BMP to PNG
Convert BMP to PNG Online — Lossless & Much Smaller
Compress an uncompressed bitmap losslessly — every pixel identical.
About BMP to PNG
A BMP stores pixels essentially raw — three or four bytes each, with no compression worth the name — which is why a plain screenshot arrives as tens of megabytes. PNG stores the same pixels and compresses them losslessly, so this is the rare conversion with no trade-off in it: the file gets substantially smaller and not a single pixel changes. That makes it the right conversion for anything where the pixels matter — a screenshot with text in it, a scanned line drawing, an exported interface mock, a sprite sheet out of an old tool. Converting the same BMP to JPG would make it smaller still, but JPG is lossy and puts ringing around every hard edge, which is precisely what this class of image is made of. How much smaller depends entirely on the picture. Flat colour, large blocks and repeated rows compress enormously; a photograph saved as BMP compresses far less, because photographic noise is not redundant. So this page promises no percentage: it shows the byte count before and the byte count after, and you can read the answer for your own file. A BMP carrying an alpha channel keeps it, since PNG has one too. Batch conversion is supported, and the file never leaves this tab.
Questions
Will the PNG really be smaller?
Almost always, and by a lot. A BMP stores each pixel's bytes with no compression at all — a 12-megapixel image is over 36 MB — while PNG runs the same pixels through filtering and deflate. Photographs shrink least because their pixels are noisy; screenshots, diagrams and anything with flat colour shrink dramatically. The page shows the IN and OUT byte counts, so the number you see is your file's, not an average.
Does anything change in the picture?
No. PNG is losslessly compressed, so every pixel that came out of the BMP goes into the PNG unchanged — this is a re-packing, not a re-encoding. That is the whole appeal of this pair: the file gets much smaller and there is no quality setting to get wrong, because there is no quality decision to make.
Why not convert to JPG instead?
Because JPG throws detail away to get its size, and most BMPs are exactly the material that shows it — screenshots, UI captures, scanned line art, images with sharp edges and flat colour. If your BMP is a photograph and you want the smallest possible file, BMP to JPG is the right page and will beat PNG comfortably. For everything else, PNG is smaller than the BMP and identical to it.
Where do BMP files still come from?
Legacy Windows software, screenshots from older tools, some scanner drivers, medical and industrial capture devices, and embedded systems that could not afford a decoder. They are rarely chosen deliberately any more — a BMP usually turns up because something old wrote it, which is also why it usually needs converting before anything modern will accept it.
Can I convert a PNG back to BMP here?
Not here — browser canvas encoders cannot write BMP, and asking one for it silently produces PNG bytes wearing a .bmp name. So BMP works as an input format only. If you need a lossless copy that everything can open, PNG already fills that role at a fraction of the size.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and WebAssembly. Your files never leave your device — there is no server, no upload, no cloud processing.