Convert BMP to PNG — Free BMP to PNG Converter

How to Convert BMP to PNG

Why Convert BMP to PNG?

BMP files are uncompressed and take up far more disk space than necessary. Converting to PNG gives you lossless compression — every pixel stays exactly the same, but the file is typically 3–5 times smaller. PNG also adds transparency support that BMP lacks.

PNG is the modern standard for lossless images. Browsers, editors, and operating systems all read it without help. If you have screenshots, diagrams, or graphics in BMP format, PNG is the natural upgrade with no quality compromise.

LeanImg re-encodes the bitmap locally. The file is opened by code running inside your browser, and the finished PNG goes straight to your downloads folder — at no point does the image cross the network.

Where some quality loss is acceptable and size matters more, BMP to JPG produces far smaller files. The PNG output can also be run through our lossless compressor.

Compress your PNG · BMP to JPG

What changes going from BMP to PNG

Nothing about the picture changes in this direction, only how it is stored. The browser decodes the BMP, LeanImg's bundled decoder takes over for files the browser rejects, and the pixels are written out as an 8-bit PNG and then handed to oxipng, which rewrites the file more compactly without altering a single sample. That pass can store a 256-colour BMP as an indexed PNG again rather than as a bloated true-colour one.

A 24-bit BMP, which is nearly all of them, becomes a fully opaque PNG; transparency only appears in the output when the BMP genuinely stored some, and the converter adds none. The PNG carries no resolution, no profile and no text chunks, because the BMP had nothing of the sort worth carrying, and there is no quality slider to consider since neither format has a lossy mode.

Size depends entirely on content. Flat graphics with large single-colour areas, the classic Windows screenshot, shrink dramatically, often by an order of magnitude; a photographic BMP or a noisy scan loses far less, since deflate cannot find much to repeat. Don't bother when the file is headed for a Windows program that insists on .bmp, such as an installer or an embedded toolchain, and don't expect PNG to fix a BMP that was itself saved from a JPEG: the artefacts are already in the pixels, and a lossless target keeps them faithfully.

BMP vs PNG

What is a PNG file?

PNG became a W3C Recommendation in October 1996, designed after Unisys began enforcing the LZW patent that GIF relied on. It is lossless and only lossless: one compression method, deflate, applied after per-scanline filters. Every tool advertising a lossy PNG is really quantizing to a 256 color palette before writing an ordinary lossless PNG. Transparency comes in three grades: a real alpha channel at 8 or 16 bits, up to 256 alpha levels from a palette table, or a single keyed color.

How to open a PNG file

Nothing needs installing anywhere: Preview and Quick Look on macOS, Photos and Paint on Windows, and libpng as a base dependency on Linux mean GIMP, Krita and every GTK or Qt application read it. The interesting tools are the optimizers — optipng, oxipng and zopflipng rewrite the file losslessly, and LeanImg's compressor runs oxipng at optimization level 3 without ever changing a pixel.

Convert other formats to PNG

Convert BMP to other formats

• BMP to JPG

Frequently Asked Questions