Convert BMP to ICO online

To convert BMP to ICO, upload the BMP file, start the conversion and download the result: Converter.now writes an ICO icon with the standard sizes (16 to 256 px) that fit within the source.

◈ Encrypted transfer◷ Short retention⊘ No watermark◎ Works on every device

BMP to ICO at a glance

Converts: BMP raster image → ICO raster image
Output: An ICO icon with the standard sizes (16 to 256 px) that fit within the source
Compression: BMP: uncompressed → ICO: lossless
Engine: Pillow (with ImageMagick fallback)
Privacy: Private download link; files are deleted after 6 hours. No account needed.

Pixel decoding and image re-encoding: How BMP becomes ICO

A broadly understood bitmap with straightforward pixel storage and little compression is decoded into a working pixel canvas first, then written back out under ICO's own color and compression model. Dimensions can stay exactly the same even as encoding, metadata, and fine detail change underneath. BMP input derives row direction, stride, pixel masks, palette, bit depth, compression mode, dimensions, and optional alpha from its bitmap headers. The ICO destination is a Windows icon resource, where useful delivery normally requires a deliberate set of square raster sizes rather than one arbitrary canvas.

Canvas decoded from a broadly understood bitmap with straightforward pixel storage and little compression. Image written as a Windows icon container that can hold several square pixel sizes and color depths.

Need a different output? See all BMP conversion options, or check which other files convert to ICO.

If you want the reasoning behind this BMP to ICO route, JPG, PNG, WebP and AVIF compared explains how transparency, detail and browser support decide the format.

BMP

BMP raster image

Used for pixel-based artwork, scans, and photographs.

Family: Images
MIME: image/bmp

→

ICO

ICO raster image

Designed for pixel-based artwork, scans, and photographs.

Family: Images
MIME: image/vnd.microsoft.icon

When to actually choose BMP to ICO

ICO wins this route whenever its specific mix of compatibility, alpha, animation, and file size fits the destination better than BMP does.

What changes between the BMP model and the ICO deliverable

The source stores a broadly understood bitmap with straightforward pixel storage and little compression; the destination stores a Windows icon container that can hold several square pixel sizes and color depths. Compare application metadata after that structural change.
BMP and ICO use different metadata conventions, so application-specific fields should be treated as optional until verified.

Reading BMP correctly and satisfying what ICO expects

What can fail when BMP raster image is interpreted

BMP derivatives are often much larger than web images and may encode alpha or row order differently between apps.

What ICO raster image cannot safely promise

A conversion may create only one size, making the icon look soft in menus or high-density displays.

How the ICO writer handles this route

a Windows icon container that can hold several square pixel sizes and color depths is what gets written, labeled as image/vnd.microsoft.icon. Whether that actually opens depends on the receiving application, not on the file extension.

Acceptance evidence for the converted ICO

Record the BMP evidence before conversion

Confirm dimensions, color depth, orientation, and whether the receiving app reads transparency.

Test the ICO file in its receiving workflow

Inspect the embedded sizes and preview the icon at 16, 32, 48, and 256 pixels where required.