CONVERT
BMP → PNG
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Convert uncompressed BMP images to efficiently compressed PNG format.
BMP files store every pixel as raw, uncompressed RGB or RGBA data — no codec, no algorithm, just a flat raster dump with a small DIB header describing width, height, bit depth, and color table. The result is files that are enormous relative to their visual content: a 1920×1080 image at 24-bit color sits at roughly 6 MB before anything touches it. PNG applies DEFLATE compression (a lossless LZ77 + Huffman scheme) to the same pixel data and typically brings that same image down to 1–3 MB with zero change to any pixel value. Converting BMP to PNG is therefore one of the few format conversions where nothing is sacrificed: the output is a pixel-for-pixel identical image in a container that browsers, operating systems, and design tools all handle natively. The main driver for this conversion is practical: BMP is rejected or handled poorly by virtually every web stack, CMS, and image delivery pipeline, while PNG enjoys universal support across Windows, macOS, Linux, iOS, Android, and every current browser. Developers working with Windows GDI or legacy screen-capture tools frequently end up with BMP files that need to enter a modern workflow, and BMP-to-PNG is the standard first step.
BMP Image
Source formatBMP is an uncompressed raster image format native to Windows. Files are large but preserve exact pixel data with no compression artifacts. Rarely used on the web due to file size.
PNG Image
Target formatPNG is a lossless image format that supports transparency. It is ideal for graphics, logos, screenshots, and any image where preserving exact pixel data is important.
Why convert BMP to PNG
BMP has no native browser support in HTML img tags and is blocked by most CMS upload validators, CDN image processors, and social platforms. Windows screenshot tools, older scanning software, and some embedded systems still emit BMP by default. Beyond compatibility, raw BMP at 24 or 32 bits per pixel produces files several times larger than the equivalent PNG, which matters when emailing assets, uploading to Git repositories, or distributing UI resources. If the source BMP carries a 32-bit pixel format with an alpha channel, PNG preserves that transparency faithfully — something JPEG cannot do, making PNG the correct lossless target for icons, UI sprites, and diagrams that need a transparent background.
HOW TO CONVERT
BMP → PNG
Drop the BMP file
Drag and drop or click to upload your BMP. The image is transferred securely over HTTPS and queued for conversion.
Re-encode with ImageMagick
ImageMagick decodes every pixel of the BMP and writes a matching PNG with sensible default quality settings.
Download the PNG
The converted PNG is ready to download as a single file; both files delete automatically within two hours.
Common Use Cases
Share across platforms
Send PNG files to anyone without worrying about whether they have the right software for BMP.
Embed in documents
Drop PNG output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
PNG often produces smaller files than BMP for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
BMP vs PNG — Strengths and limitations
What each format does best, and where it falls short.
BMP Strengths
- Dead-simple format — trivially easy to read and write.
- Lossless and uncompressed — perfect bit-exact pixel storage.
- Universally supported in Windows applications since 1985.
- Supports 1, 4, 8, 16, 24, and 32-bit color depths.
Limitations
- Enormous file sizes — no meaningful compression in typical use.
- Not a web format — browsers support it but nobody serves BMPs over HTTP.
- No metadata support (no EXIF, no ICC profile in practice).
PNG Strengths
- Lossless compression — every save preserves the original pixels perfectly.
- Full 8-bit alpha channel for smooth transparency.
- Excellent for text, UI screenshots, logos, and line art.
- Royalty-free and an ISO standard (ISO/IEC 15948).
- Supports 16-bit color depth for high-fidelity work.
Limitations
- Much larger than JPEG for photographs (no perceptual compression).
- No native animation in most software (APNG support is inconsistent).
- No CMYK support — web and screen only, not print.
BMP vs PNG — Technical specifications
Side-by-side comparison of the technical details.
BMP
- MIME type
- image/bmp
- Extensions
- .bmp, .dib
- Compression
- None (typical); RLE 4/8 bit (rare)
- Color depths
- 1, 4, 8, 16, 24, 32 bits per pixel
- Byte order
- Little-endian
PNG
- MIME type
- image/png
- Compression
- Lossless — DEFLATE (zlib)
- Color depth
- 1, 2, 4, 8 or 16 bits per channel
- Max dimensions
- 2^31 − 1 pixels per side (2.1 billion)
- Transparency
- Full 8-bit alpha channel
- Standard
- ISO/IEC 15948:2004
| Specification | BMP | PNG |
|---|---|---|
| MIME type | image/bmp | image/png |
| Extensions | .bmp, .dib | — |
| Compression | None (typical); RLE 4/8 bit (rare) | Lossless — DEFLATE (zlib) |
| Color depths | 1, 4, 8, 16, 24, 32 bits per pixel | — |
| Byte order | Little-endian | — |
| Color depth | — | 1, 2, 4, 8 or 16 bits per channel |
| Max dimensions | — | 2^31 − 1 pixels per side (2.1 billion) |
| Transparency | — | Full 8-bit alpha channel |
| Standard | — | ISO/IEC 15948:2004 |
BMP vs PNG — Typical file sizes
Approximate file sizes for common scenarios.
BMP
- Small icon (32×32) 4 KB
- Screenshot (1920×1080) ~6 MB
- 4K image (3840×2160) ~25 MB
- Scanned A4 at 300 dpi ~25 MB
PNG
- Icon or small logo 2–20 KB
- UI screenshot (1920×1080) 200–800 KB
- High-res photo (12 MP) 10–30 MB
- Print-ready illustration 5–50 MB
Quality & Compatibility
BMP-to-PNG is a fully lossless conversion. DEFLATE operates on the filtered pixel stream and reconstructs it identically on decode, so peak signal-to-noise ratio is infinite — no rounding, no quantization, no chroma subsampling. Bit depth is preserved: 1-bit (monochrome), 4-bit, 8-bit indexed, 24-bit RGB, and 32-bit RGBA BMP variants all map to a corresponding PNG color type and bit depth without promotion or demotion. The one metadata consideration is that BMP stores horizontal and vertical resolution in pixels-per-meter inside its DIB header; PNG stores resolution in a pHYs chunk using pixels-per-unit with a unit flag. KaijuConverter carries that resolution value across during the conversion. BMP has no concept of gamma correction or ICC color profiles; PNG supports both (gAMA and iCCP chunks), but since the source carries neither, the output PNG will likewise omit them, leaving color management to the viewing application's default assumption.
Tips for Best Results
- If your BMP is 32-bit (sometimes written as BMP with alpha by GDI+ or the Windows snipping tool), verify the output PNG actually has a transparent background by opening it in a browser tab or an image editor before deleting the original — some BMP encoders write 32-bit files with the alpha channel set entirely to 255 (fully opaque), so the transparency may appear correct in PNG but was never real to begin with.
- For batch conversions of BMP screenshots or UI assets intended for web use, check whether your BMPs are 96 DPI (the Windows default). If downstream tools like Figma or Adobe XD need a specific resolution, adjust the pHYs chunk in the PNG after conversion rather than relying on the BMP header value, which may not match your design grid.
- PNG compression level does not affect pixel data, only encode time and file size. If you are converting many large BMP files and the resulting PNGs will be served through a CDN that applies its own compression (Cloudflare Polish, AWS CloudFront, etc.), a moderate DEFLATE level is sufficient — the CDN will re-optimize anyway, and you avoid the CPU cost of maximum compression on files that will be reprocessed.
Frequently Asked Questions
It depends on the codecs involved. If both BMP and PNG are lossy, the pixels are re-encoded and a small amount of detail is discarded — invisible at default quality settings on photographs. If PNG is lossless (PNG, TIFF, BMP) the output keeps every pixel of the decoded BMP exactly, but cannot recover detail that BMP had already compressed away.
Often yes, especially when PNG is lossless. BMP tuned for efficient web delivery will usually produce smaller files than PNG's default settings. If file size matters, drop the quality in Advanced or pick a more compressed target format instead.
KaijuConverter uploads over HTTPS, processes the image in an isolated container and deletes both the source and the output within two hours. No account is required, file contents are never logged, and we do not use uploads to train any model. For confidential material, the paid plan includes a data-processing agreement.
RELATED CONVERSIONS
Other popular pairs involving BMP or PNG
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Related comparisons
See these formats side by side to understand which fits your use case best.
Related Guides
BMP Bitmap Format: The Complete Technical Guide
Everything about the BMP format: DIB header variants, pixel storage, color depths (1 to 32-bit), RLE compression, alpha channels, and BMP vs PNG vs TIFF.
Read guideBMP Format: Windows Bitmap Images Explained — Headers, Compression & Use Cases
Learn what BMP files are, how the Windows Device Independent Bitmap format works, supported colour depths, compression options, and when to use BMP vs PNG.
Read guidePNG: Advanced Color Modes, Filtering & Compression Strategies
Comprehensive guide to PNG encoding: color types (indexed, grayscale, RGB, RGBA), scanline filtering (Sub/Up/Average/Paeth), CRC checksums, gamma correction, ICC color profiles, interlacing methods.
Read guideSecure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.