ICO to BMP Converter

What Is the ICO to BMP Converter?

This tool converts a Windows .ico icon file to BMP entirely in your browser. ICO is a container format built for Windows icons and website favicons -- a single .ico file can bundle several resolutions of the same image (e.g. 16×16, 32×32, 256×256) so the operating system or browser picks whichever fits. This tool reads the real ICO byte structure and extracts the largest embedded image, then re-encodes it as BMP.

How to Use This Tool

Click the upload area and choose an .ico file. The converted preview appears immediately; click Download to save it as a real BMP file.

Need to go the other way? Use the BMP to ICO tab above, or open the BMP to ICO converter directly.

Why Convert ICO to BMP

BMP is a far more widely supported, general-purpose image format than ICO -- most photo editors, social platforms, and websites don't accept .ico uploads at all, so converting to BMP is usually the first step to actually using an icon's artwork somewhere else (editing it, sharing it, or repurposing a favicon's image as a regular graphic).

What This Converter Writes

After extracting the largest embedded image from your .ico file, the tool builds a BMP file by hand rather than using the browser's encoder, because browsers cannot save canvases as BMP. The result is an uncompressed 24-bit file: a 14-byte file header, a 40-byte info header, and then the pixels stored bottom row first in blue-green-red order. Each row of pixel data is padded so its length is a multiple of four bytes.

Predicting the File Size

Because nothing is compressed, you can calculate the size yourself. Each pixel takes 3 bytes, each row is rounded up to a multiple of 4 bytes, and 54 bytes of header are added.

• A 32x32 icon: 96 bytes per row x 32 rows = 3,072, plus 54 = 3,126 bytes.
• A 256x256 icon: 768 bytes per row x 256 rows = 196,608, plus 54 = 196,662 bytes.
• A 33x33 icon: 99 bytes per row rounds up to 100, so 100 x 33 = 3,300, plus 54 = 3,354 bytes.

That last case shows the row padding at work. The tool also displays the output size after conversion, which you can check against this formula.

Transparency Is Dropped

This BMP has no alpha channel. The tool flattens the icon onto white and then writes the red, green and blue values of every pixel. BMP has no alpha channel, so transparent pixels of the icon are flattened onto white before the file is written. Semi-transparent edges, such as soft shadows, are blended with white.

If your icon has transparency and you need a specific background color, add it in an image editor first, or convert to PNG and flatten it there.

When a BMP Is Useful

• Old Windows software or embedded devices that read only plain bitmaps.
• Workflows that need raw, uncompressed pixel data without compression artifacts.
• Testing or teaching, where the simple structure of BMP is helpful.

For everyday sharing, BMP is a poor choice because the files are large compared with PNG for the same image. Use it only when a program specifically asks for it.

Sizing Expectations

The BMP has the same pixel dimensions as the largest image in the .ico, and nothing is upscaled. If the icon only contains small sizes, the bitmap will be small as well.

Frequently Asked Questions