Convert BMP to ICO — Free Online Converter

ICO is the Windows icon file format, storing multiple image sizes (16x16, 32x32, 48x48) in a single container for crisp display across all Windows UI contexts. Converting BMP to ICO is a natural fit — BMP and ICO share deep roots in the Windows ecosystem, and ICO originally stored its image entries as embedded BMP data. This conversion creates a proper multi-size icon from your BMP source, suitable for application executables, desktop shortcuts, and favicons.

BMP's uncompressed 24-bit color provides excellent source quality for icon generation. The raw pixel data is downscaled to standard icon sizes using high-quality Lanczos resampling, producing sharper results than compressed source formats. The main limitation is that standard BMP does not carry alpha transparency, so the resulting icons will be fully opaque without transparent backgrounds.

Windows application development requires ICO format for executable icons, taskbar entries, and Start Menu pins. If you have a logo or brand graphic stored as BMP — common in legacy Windows development environments — converting to ICO is the required step for embedding it in your application. Resource compilers (rc.exe), Visual Studio, and installers all expect ICO format.

Website favicons benefit from ICO format for maximum browser compatibility, particularly in corporate environments running older Internet Explorer versions. A BMP logo converted to ICO with 16x16 and 32x32 embedded sizes covers both the browser tab icon and bookmark requirements.

Sharp decodes the BMP's uncompressed 24-bit pixel data and generates ICO-standard sizes: 16x16, 32x32, and 48x48 pixels using Lanczos resampling. Each size is embedded as a separate entry in the ICO container. Since standard BMP does not carry alpha transparency, the icons are fully opaque. The ICO file uses the to-ico package for proper container generation with directory headers and per-size bitmap data.