Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Convert a BMP image to ICO instantly, right in your browser.
Upload a BMP file to convert it to ICO.
This tool converts a Windows Bitmap image to Windows Icon entirely in your browser -- the file is decoded, redrawn onto a canvas, and re-encoded as ICO without ever being uploaded to a server. BMP (Windows Bitmap) stores pixel data with little to no compression, so files are typically several times larger than an equivalent JPG, PNG, or WebP. It's mostly encountered from older Windows software, some scanning/printing tools, and a handful of legacy enterprise systems -- rarely a good format to actually publish or email as-is.
Click the upload area and choose a BMP file. The converted preview appears immediately; click Download to save it as a real .ico file.
Need to go the other way? Use the ICO to BMP tab above, or open the ICO to BMP converter directly.
The most common reason to convert a BMP into ICO is building a favicon or a Windows app icon -- most platforms that ask for a favicon file specifically want a real .ico, not a renamed PNG/JPG. ICO is the Windows icon/favicon format. This tool embeds your source image as a single-size PNG-in-ICO container (the same approach browsers themselves accept for a site favicon) rather than the old multi-resolution ICO bundles image editors sometimes produce.
The tool decodes your BMP with the browser, draws it onto a canvas at its original pixel width and height, encodes that canvas as PNG, and wraps the PNG in an ICO container. Bitmaps up to 256 by 256 keep their exact dimensions; larger ones are scaled down to fit. The result panel shows the pixel dimensions and the original file size followed by the resulting ICO size. This is often a big reduction, because a BMP stores raw pixels while the PNG inside the ICO is compressed without losing anything.
Imagine a 256 by 256 BMP exported from an old design program. Uncompressed, a 24-bit bitmap of that size is roughly 192 KB, while the ICO produced here may be only a few kilobytes if the artwork is simple. Flat colors and logos compress especially well. The dimensions stay 256 by 256 in the output, and the icon is opaque wherever the bitmap was opaque.
Most BMP files do not carry a transparency channel, so the resulting icon will usually have a solid background, such as a white or colored rectangle behind your artwork. If you want a transparent icon, first remove the background in an image editor and save as PNG, then use the PNG to ICO converter instead. Some BMP variants with alpha data may be decoded differently by different browsers, so always check the preview, which is drawn over a checkerboard to help you spot transparency.
The tool has an ICO to BMP tab as well. For a real .ico file, it reads an embedded PNG image from the icon (picking the largest PNG-based entry) and then encodes it as a bitmap. Icons that store only older bitmap-style entries may not be readable, and the tool then explains that it could not read an image out of the file.
No -- the whole conversion happens locally in your browser using the Canvas API. Your file never leaves your device.
There's no artificial limit in the tool itself, but very large images take longer to process since everything runs in your browser rather than on a server.
BMP files store pixels with little or no compression, while the PNG inside the ICO is compressed losslessly. The picture content is the same, just stored more efficiently.
Usually not, because most BMP files have no transparency information. Remove the background in an editor and use a PNG source if you need transparency.
Use a square image at the size you want the icon, such as 256 by 256 or a size recommended by your platform. Only images larger than 256 pixels on a side are scaled down.
It is a standard single-image PNG-in-ICO file, which is the type browsers accept for favicons. Check your platform's recommended size and upload requirements.
BMP and ICO aren't interchangeable: BMP works well for legacy Windows software and pipelines that need raw, uncompressed pixels, whereas ICO is the better fit for favicons and Windows application icons.
| BMP | ICO | |
|---|---|---|
| File extension | .bmp | .ico |
| Compression | usually none (uncompressed) | a container holding PNG or BMP images |
| Transparency | No transparency | Full transparency (alpha channel) |
| Animation | Single image | Single image |
| Colours | 16.7 million (24-bit as written here) | up to 32-bit colour with alpha |
| Best for | legacy Windows software and pipelines that need raw, uncompressed pixels | favicons and Windows application icons |
| Support | Windows and most editors; browsers open it but it is rarely used on the web | all browsers for favicons and Windows for icons |
The conversion happens in your browser; the file is never uploaded.