BMP vs PNG: What's the Difference?
BMP and PNG are both lossless formats — they store your image without throwing away pixel data. But that's nearly where the similarity ends. BMP is a legacy Windows format from the 1980s; PNG is a modern, open standard built for the web. Knowing the difference will save you from inflated file sizes and compatibility headaches.
What is BMP?
BMP (Bitmap Image File) is a raster image format developed by Microsoft for early versions of Windows. It stores raw pixel data in a grid, mapping each pixel directly to its RGB color values with virtually no compression.
- Pros: Maximum fidelity (no compression whatsoever), universal compatibility on Windows systems, trivially simple format for software developers to read and write.
- Cons: Enormous file sizes, no alpha transparency in standard 24-bit BMP, no web browser support, almost no metadata support.
The "optional" RLE compression in BMP is rarely used in practice and only applies to 8-bit (256 color) images — essentially irrelevant for modern photography or design work.
What is PNG?
PNG (Portable Network Graphics) was created in 1995 as a patent-free replacement for GIF. It uses DEFLATE lossless compression, which can reduce file size by 20–70% with zero quality loss.
- Pros: Dramatically smaller than BMP, full alpha transparency support, web-native (loads in any browser), widely supported across all operating systems and image editors.
- Cons: Larger than JPEG or WebP for photographs, no CMYK support for print.
File Size Comparison
This is where BMP falls hardest. Raw pixel counts are relentless:
- A 1920×1080 24-bit BMP is exactly 5.93 MB — every time, uncompressed.
- The equivalent PNG is typically 500 KB – 1.5 MB (depending on image complexity).
- The equivalent WebP is typically 150 KB – 400 KB.
For a single image that difference may seem manageable. But a folder of 100 product photos at 6 MB each means 600 MB as BMP — versus 50–100 MB as PNG. Format choice compounds quickly at scale.
Transparency Support
Standard 24-bit BMP has no alpha channel. The format does define a 32-bit variant with an alpha channel, but support is inconsistent across applications and operating systems. Many programs that claim to open BMP files simply ignore the alpha data.
PNG, on the other hand, has first-class 8-bit alpha transparency built into the core specification. Semi-transparent edges, drop shadows, and partially transparent layers all render correctly in every PNG-compatible application.
If you need transparency, PNG wins unconditionally.
When to Use BMP
BMP's use cases have been reduced significantly by modern formats, but it remains relevant in a few specific contexts:
- Legacy Windows applications: Some older software only accepts BMP input.
- Embedded and hardware systems: Certain microcontrollers, industrial displays, and embedded firmware use BMP because its simple structure is trivial to parse with minimal code.
- ICO icon source files: Windows icon creation tools often accept BMP as source input before packaging into
.icoformat. - Internal software pipelines: Bitmap buffers in video games or image processing pipelines sometimes use BMP as an intermediate format before final export.
When to Use PNG
For every other use case, PNG is the better choice:
- Web and mobile: Logos, UI assets, screenshots, illustrations — anything displayed on a screen benefits from PNG's compression and transparency.
- Design and editing: PNG is the export format of choice from Figma, Photoshop, Illustrator, and Sketch.
- Archiving screen graphics: If you need a lossless screen capture, PNG gives you the same quality as BMP at a fraction of the size.
- Any file that will be transmitted: Email, cloud storage, messaging — smaller files are always better.
Converting BMP to PNG
Converting BMP to PNG is lossless — since BMP stores raw pixels and PNG simply compresses those same pixels, the conversion produces an identical image at a much smaller file size. There is nothing to "lose" in the conversion.
You can convert BMP files to PNG instantly using our free online tool. Upload your BMP, and download a PNG that looks identical but is typically 70–90% smaller.