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BMP
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ICO

BMP to ICO Converter — Free, Online, No Upload

Got a BMP logo from a legacy Windows project? Turn it into a proper multi-resolution ICO for modern Windows or the web.

Free · no signup2 free files a day100% in-browser · no upload

Tap to select BMP files

or click to browse

2 free files per day (2 left today) · Up to 10 MB each · Upgrade for more

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✓ Files never uploaded✓ 100% browser-based✓ No account required

How to convert BMP to ICO online

  1. 1

    Drop your BMP file

    Drag your Bitmap Image File file onto the box above, or click it to pick a file.

  2. 2

    Wait a few seconds

    Conversion starts on its own and runs on your device, not on a server.

  3. 3

    Download your ICO

    Click Download to save the Windows Icon Format file.

BMP vs ICO: format overview

BMP

Bitmap Image File

Microsoft · 1987

Compression
none
Transparency
No
  • ✓ No compression — original pixel data preserved
  • ✓ Universal Windows support
  • ✗ No compression = massive files
ICO

Windows Icon Format

Microsoft · 1985

Compression
lossless
Transparency
Yes
  • ✓ Multiple resolutions in a single file
  • ✓ Required format for Windows app icons and favicons

BMP magic bytes: 42 4D

ICO magic bytes: 00 00 01 00

Why convert BMP to ICO?

BMP files are sometimes used for image assets in older Windows application development — resource editors, legacy toolkits, and older versions of Visual Studio worked heavily with BMP for icon source images. To use those BMP images as application icons or favicons, they need to be converted to ICO format, which is what Windows and browsers actually use.

ICO is a container that holds one or more image sizes. Windows uses different sizes depending on context: 16×16 for the taskbar, 32×32 for desktop icons, 48×48 for file explorer large icons, and 256×256 for high-DPI displays. Converting a BMP to ICO handles both the format conversion and the generation of multiple size variants from the source image.

For best results, the BMP should be a square image with the icon graphic centered; a non-square BMP is fitted inside the square with transparent bands, not stretched. Complex photographic BMPs don't translate well to icon sizes — detail disappears at 16×16 pixels. Simple graphics, logos, symbols, and high-contrast images work well. BMP files rarely carry transparency, so the icon keeps the BMP's background colour at every size. For a transparent icon, start from a PNG instead.

Quality & file size: BMP to ICO

Typical sizes: BMP 35–40 MB (12MP photo); ICO 10–100 KB (multi-size icon).

Both formats keep every pixel, so the ICO looks the same as the BMP.

Frequently asked questions

What BMP size should I start with?
Use at least a 256×256 pixel BMP and crop it to a square before converting. The converter scales down to the standard ICO sizes (16, 32, 48 px) and a larger source produces better-quality small frames.
Can I use a BMP with a background colour as a transparent ICO?
Not automatically. BMP without an alpha channel will produce an ICO with that background colour. For a transparent favicon, start from a PNG with transparency instead.

Your BMP file never leaves this tab — FormatDrop has no endpoint that receives file data. How it works