Convert BMP to ICO
Icon artwork that has been sitting in a legacy Windows project is very often a bitmap, and turning it into a proper ICO is what lets Windows, a browser or an installer actually use it as an icon. Historically the two formats are close relatives: the ICO container was designed around BMP pixel data, which is why the conversion feels so natural.
Drop your BMP files below and download ICO in seconds. Free, unlimited and completely private: the conversion runs inside your browser, so your files never leave your device and are never uploaded to a server.
No upload. Works with your network switched off. Check it yourself, or read what actually happens to your file.
Why convert BMP to ICO?
There is one catch worth knowing before you start, and it is the reason many BMP-derived favicons look wrong. A standard 24 bit BMP has no alpha channel, so there is no transparency to carry into the icon. Whatever background colour is baked into the bitmap, usually white, becomes a solid rectangle behind your icon in the tab bar or on the desktop. If you need the icon to sit on a transparent background, start from a PNG or an SVG instead.
BMP stores pixels with little or no compression, which makes files huge but trivially simple to read. It is mostly seen in legacy Windows workflows, screenshots from older tools and some scientific software. Converting to a compressed format usually shrinks a BMP by 90 percent or more.
ICO files bundle one or more icon sizes into a single file that Windows and browsers use for favicons and app icons. Regular image viewers often refuse to open them, and most editors cannot save them, so a converter is the practical way in or out of the format.
What this converter does to your BMP file
The BMP is decoded and, if it is larger than 256 pixels on either side, scaled down proportionally to fit within 256 x 256, the maximum a single ICO entry allows. It is then written as a 32 bit PNG-compressed entry inside the ICO container rather than as raw BMP data, a form Microsoft's icon documentation notes is supported from Windows Vista onward. Because the source BMP has no alpha channel, the icon is fully opaque. Tick Resize width first if you want a specific size such as 32 or 48 pixels.
BMP vs ICO at a glance
| BMP | ICO | |
|---|---|---|
| Full name | Bitmap image | Windows icon |
| Compression | Uncompressed | Contains PNG or BMP data |
| Transparency | No | Yes |
| Best for | Legacy Windows software and raw pixel data | Favicons and Windows application icons |
What changes when you convert BMP to ICO
| What happens | |
|---|---|
| Image quality | Depends on the quality setting above, which controls how much detail ICO keeps. |
| Transparency | BMP has no alpha channel, so there is no transparency to lose. |
| EXIF and GPS | Removed. The conversion goes through a pixel buffer, so camera data and location are not carried into the ICO file. |
| Colour profile | Not carried across. The image is handled in sRGB, which is right for the web and wrong for colour-managed print work. |
| Animation | Not applicable. BMP files here are single images. |
| File size | Varies with the content of the image. No figure is quoted here, because none has been measured on a documented test set. |
How to convert BMP to ICO
- Drop one or more BMP files into the box above, or click to browse.
- ImageConvert converts each file to ICO right on your device.
- Download a single file, or grab everything at once as a zip.
Frequently asked questions
Will the icon have a transparent background?
No. A standard 24 bit BMP stores no alpha channel, so there is nothing transparent to preserve and the icon keeps whatever solid background the bitmap had. Convert from a PNG or SVG if you need transparency.
What size icon do I get?
Up to 256 x 256, the maximum a single ICO entry supports. Anything larger is scaled down proportionally. Tick Resize width and enter a value first if you want a specific size such as 16, 32 or 48 pixels.
Can I use the result as a favicon?
Yes. It is a standard ICO file, so placing it at the root of your site as favicon.ico works in every browser. Just be aware of the opaque background, which is very visible against a dark browser theme.
What is a BMP file?
BMP is an uncompressed Windows bitmap that keeps full pixel detail at a large file size.
What is an ICO file?
ICO is the Windows icon format, used for favicons and application icons.
Is it free to convert BMP to ICO?
Yes. There are no limits, no watermarks and no account needed. Convert as many BMP files as you like.
Are my files private?
Completely. Your BMP files never leave your browser and are never uploaded to a server, so your images stay on your device.