Free online BMP to ICO converter

Windows applications, folders, and shortcuts require ICO files for their icons, while BMP files are ordinary raster images. Converting a BMP is useful when an existing bitmap must be assigned as a Windows icon, packaged as a favicon, or edited into an ICO containing several display sizes.

What the BMP format is

BMP stores raster pixels, usually with little or no compression. Common color depths include 1-, 4-, 8-, 16-, 24-, and 32-bit, and BMP can contain color-table, true-color, and limited RLE-compressed data. Microsoft Paint, Windows utilities, older graphics applications, scanners, legacy projects, and uncompressed image archives commonly use BMP.

BMP is straightforward to read but usually produces larger files than PNG or JPEG because it lacks efficient general-purpose compression. A BMP is an image, not an icon container, so it normally contains only one image at one size.

What the ICO format is

ICO is the Windows icon container format used for application executables, desktop shortcuts, folders, and favicon files. One ICO file can contain multiple square image entries, commonly 16×16, 32×32, 48×48, 64×64, 128×128, and 256×256, allowing software to choose a suitable size instead of scaling one image repeatedly.

ICO entries can use palette or true-color data and can include an alpha channel for transparency. Newer Windows software accepts PNG-compressed entries inside ICO files, which reduces file size; older software may require traditional uncompressed entries.

Convert BMP to ICO online

1. Open the BMP-to-ICO converter on 101convert.com.
2. Upload the BMP file and select ICO as the output format.
3. Start the conversion and download the resulting .ico file.
4. Test the file by assigning it to a Windows shortcut or opening it in an icon editor.

This option requires no software installation. Avoid uploading confidential or sensitive images to any web-based converter; use a desktop method instead.

Convert with ImageMagick

1. Install the official desktop distribution of ImageMagick and confirm that the magick command works in a terminal.
2. Place the source file, such as logo.bmp, in a convenient folder.
3. Run this command from that folder:
   magick logo.bmp -define icon:auto-resize=16,32,48,64,128,256 logo.ico
4. Open logo.ico in an icon editor or assign it to a shortcut to verify the entries.

The icon:auto-resize definition creates multiple icon sizes from the source. For one 32-pixel entry, use magick logo.bmp -resize 32x32 logo.ico. A multi-size ICO is generally more useful than a single-size file.

Convert with GIMP

1. Open the BMP through File → Open.
2. For a single-size icon, use Image → Scale Image and set a square size such as 32 × 32 px.
3. Choose File → Export As, enter a filename ending in .ico, and select Export.
4. Use the ICO export options, if provided by the installed GIMP version, to add supported sizes or transparency. If the version exports only one image entry, use ImageMagick or a dedicated icon editor for a multi-size ICO.

Quality and compatibility limits

ICO is not a vector format. Enlarging a small BMP creates blur and jagged edges, so use a source at least as large as the biggest required entry and downsample it rather than enlarging it. Prepare a square canvas before conversion if the complete image must remain visible; otherwise, resizing may distort, crop, or pad a rectangular BMP.

A normal BMP has no transparent background. Conversion cannot determine which background pixels should become transparent unless the source already contains usable alpha data or you edit the image and designate a transparent color. For modern Windows targets, include 32-bit entries with alpha transparency and common sizes such as 16×16, 32×32, and 48×48. For older programs, include a traditional uncompressed entry as well as any PNG-compressed entries, because some legacy readers do not support PNG data inside ICO files.