CONVERT BMP → ICO (BMP to ICO)
Fast, secure BMP to ICO conversion. No registration required.
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Automatic format identification and lossless transcoding across 201+ formats.
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EXIF & Color Verification Audit ISO Verified
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GPS Coordinates (37.1773° N, 3.5986° W): Stripped (Zero Location Leak)
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Device Serial & Lens ID: Stripped (EXIF / IPTC / XMP Clean)
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Color Space Profile: Display P3 → sRGB IEC61966-2.1
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Chroma Subsampling: 4:4:4 High Fidelity (High-fidelity algorithmic conversion)
HOW TO CONVERT BMP → ICO
Upload your BMP
Start by dropping the BMP onto the uploader. Files up to 25 MB go through on the free tier without registration; paid plans go up to 2 GB.
Conversion happens server-side
Our imagemagick-based pipeline reads the BMP pixel grid, preserves resolution and colour profile, and encodes a clean ICO.
Grab the result
A download button appears as soon as the ICO is ready. Save locally or share the short-lived URL.
BMP is an uncompressed raster format that stores every pixel at full fidelity, typically at 24-bit RGB or 32-bit RGBA, with no inter-pixel compression whatsoever. ICO is Windows' native icon container format, and it is the destination format that browsers, operating systems, and installers actually read when they look for a site favicon or application icon. The conversion from BMP to ICO is therefore not a quality upgrade or a creative choice — it is a structural requirement: if you want a file that Windows Explorer, Chrome's favicon system, or an NSIS installer will recognize as an icon, ICO is the mandatory container. A raw BMP file, even one that is 32x32 pixels and 32-bit RGBA, is not recognized as an icon by any of those consumers. The ICO format wraps one or more image frames — each at a different resolution and bit depth — inside a single binary container with a directory header that identifies offsets and sizes. In practice, the most useful ICO files contain multiple embedded frames: 16x16, 32x32, 48x48, and sometimes 256x256 using embedded PNG compression rather than raw BMP data for the large frame. When you start from a BMP, you are providing a single flat raster image, and the converter must resize, crop, or embed it into that multi-resolution structure.
Why convert BMP to ICO
The practical reason a developer or designer converts BMP to ICO is that Windows and web browsers refuse to treat a BMP as an icon regardless of its pixel dimensions. Windows Shell looks for ICO or PE-embedded icon resources; most browsers look for favicon.ico at the site root and parse the ICO container header before rendering anything. BMP files also carry no transparency channel that Windows Shell can composite against the desktop background — a 32-bit RGBA BMP technically has an alpha channel in its pixel data, but Windows Explorer does not honor it in the BMP format the way it does in ICO with its AND mask or 32-bit alpha plane. ICO is thus the only interchange format that covers every Windows icon consumption point simultaneously.
BMP vs ICO — 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
- MIME Type
- image/bmp
- Extension
- .bmp
- Category
- Raster & Vector Images
- Full Name
- BMP Image
- Conversion Engine
- IMAGEMAGICK
ICO
- MIME type
- image/vnd.microsoft.icon
- Compression
- Uncompressed bitmap or embedded PNG (Vista+)
- Color depths
- 1, 4, 8, 24, 32 bits per pixel
- MIME Type
- image/x-icon
- Extension
- .ico
- Category
- Raster & Vector Images
- Full Name
- ICO Icon
- Conversion Engine
- IMAGEMAGICK
- Max resolutions per file
- 65 535 images
- Max single image size
- 256×256 px
| Specification | BMP | ICO |
|---|---|---|
| MIME type | image/bmp | image/vnd.microsoft.icon |
| Extensions | .bmp, .dib | — |
| Compression | None (typical); RLE 4/8 bit (rare) | Uncompressed bitmap or embedded PNG (Vista+) |
| Color depths | 1, 4, 8, 16, 24, 32 bits per pixel | 1, 4, 8, 24, 32 bits per pixel |
| Byte order | Little-endian | — |
| MIME Type | image/bmp | image/x-icon |
| Extension | .bmp | .ico |
| Category | Raster & Vector Images | Raster & Vector Images |
| Full Name | BMP Image | ICO Icon |
| Conversion Engine | IMAGEMAGICK | IMAGEMAGICK |
| Max resolutions per file | — | 65 535 images |
| Max single image size | — | 256×256 px |
BMP vs ICO — 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).
ICO Strengths
- Multi-resolution: one file, many sizes, OS picks the right one.
- Universal favicon support in every browser since IE5.
- Supports transparency (1-bit since 1985, full alpha since XP).
- Tiny file size — an entire favicon pack typically fits in under 15 KB.
- No licensing or patent concerns — fully in the public domain spec-wise.
Limitations
- Cannot compress continuous-tone images efficiently — use PNG or WebP for photos.
- Format is essentially frozen in 1999 — no HDR, no wide gamut, no modern features.
- Maximum image dimension is 256×256 px (inside an ICO container).
Quality & Compatibility
What is preserved: all pixel-level color data from the BMP source frame at the target resolution, including the alpha channel if your BMP is 32-bit RGBA and the ICO output uses 32-bit color depth. What is lost or altered: BMP stores pixels as uncompressed DIB data; the ICO container for the 16x16 and 32x32 frames also stores uncompressed DIB data internally, so those frames are lossless. The 256x256 frame inside a modern ICO is typically stored as a compressed PNG stream, introducing the PNG lossless compression step rather than lossy artifacts. If your source BMP is larger than 256x256, a downscale to 256x256 involves resampling — that resampling step is where actual pixel quality is determined by the algorithm used. No metadata from BMP headers such as DPI or color space tags carries over into ICO; the ICO format has no field for those values.
Tips for Best Results
- Start from a BMP that is at least 256x256 pixels with a transparent background as 32-bit RGBA — converting a 24-bit BMP without alpha means your ICO frames will have no transparency, and Windows will composite your icon against a solid color mask instead of blending it cleanly against the desktop or taskbar.
- If you only need a favicon for a website, a single 32x32 or 48x48 frame inside the ICO is sufficient and keeps the file small; the 256x256 frame matters for Windows desktop shortcuts and high-DPI displays at 200 percent scaling, so include it if the ICO will be used as an application icon rather than only a browser tab icon.
- Verify the output ICO actually contains multiple resolutions after conversion by checking the file size — a valid multi-resolution ICO with 16x16, 32x32, 48x48, and 256x256 frames will typically be between 50 KB and 120 KB; a suspiciously small file under 5 KB usually means only one frame was embedded, which will look blurry at sizes Windows did not downscale from your single frame.
Frequently Asked Questions
It depends on the codecs involved. If both BMP and ICO are lossy, the pixels are re-encoded and a small amount of detail is discarded — invisible at default quality settings on photographs. If ICO 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 ICO is lossless. BMP tuned for efficient web delivery will usually produce smaller files than ICO'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.
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.
ICO Icon
Target formatICO is the icon file format used for favicons and Windows application icons. A single ICO file can contain multiple image sizes and color depths for different display contexts.
Going the other way? Convert ICO back to BMP with the same engine.
Common Use Cases
Share across platforms
Send ICO files to anyone without worrying about whether they have the right software for BMP.
Embed in documents
Drop ICO output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
ICO 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 ICO — Typical file sizes
Approximate file sizes for common scenarios.
- Small icon (32×32) 4 KB
- Screenshot (1920×1080) ~6 MB
- 4K image (3840×2160) ~25 MB
- Classic favicon (16×16 only) < 2 KB
- Multi-size favicon pack (16/32/48/256) 5-15 KB
- Full Windows app icon set 20-100 KB
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Convert thousands of camera RAW files (CR3, NEF, ARW) to WebP, AVIF, or TIFF in one pass.
GPU-accelerated RAW development with end-to-end 16-bit ICC color profile management.
Related comparisons
See these formats side by side to understand which fits your use case best.
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