ICO to BMP

Created on 21 November, 2025 • Image Manipulation Tools • 0 views • 6 minutes read

Introduction: Understanding ICO and BMP Formats
When dealing with images for icons or legacy Windows graphics, you’ll often come across two formats: ICO and BMP. The ICO format is specifically designed for icons—small, multi-resolution images that represent applications, shortcuts, or UI elements—while BMP (bitmap) is a more general-purpose raster image format widely used for uncompressed graphics. Converting from ICO to BMP can be useful when you need a simple, flattened image without the multiple embedded sizes or transparency layers that an ICO may contain.

What Is an ICO File
An ICO file is the standard format for icons in Microsoft Windows. It is a container that can include multiple versions of an image, in different resolutions (for example, 16×16, 32×32, 256×256) and different color depths.
Wikipedia
Some of the individual images inside an ICO might be stored as BMP data, while others may use PNG compression.
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Because of this flexibility, ICO files are very efficient for representing icons that need to look good at various sizes without constantly scaling.

What Is a BMP File
BMP, or Bitmap, is a raster image format that stores image data pixel by pixel. It’s often uncompressed (though there are variants that support compression), which means BMP files can be large compared to formats like PNG or JPEG.
Lifewire
BMP is very straightforward in structure, making it easy to read and write, and therefore useful for certain applications where simplicity and speed of access are more important than file size.

Why Convert ICO to BMP
There are several motivations for converting ICO to BMP. First, BMP provides a simpler, flattened image—no multiple resolutions, no icon directory structure, just raw pixel data. This can be useful if you intend to process the image, manipulate it in a standard graphics editor, or feed it into a system that does not support ICO structures. Second, BMP is widely supported by many older or more basic tools, meaning you can open and edit the converted image easily in programs that don’t understand icon files. Third, transparency in ICO (especially via AND/XOR masks) may not translate in the same way as PNG transparency, so converting to BMP can clarify how the image will ultimately be rendered in contexts where alpha blending is not properly handled.

How to Convert ICO to BMP (Online Tools)
One of the easiest ways to perform the ICO‑to‑BMP conversion is through web-based converters. There are several free, user-friendly services:

Converter.app provides a no‑limit, browser‑based ICO-to-BMP converter that extracts all embedded sizes and outputs separate BMP files.
converter.app

ImagesTool.com also supports ICO to BMP conversion, with options to adjust image quality, size, background, and more—all in your browser.
to.imagestool.com

PhotoKit offers a secure in-browser ICO-to-BMP conversion that does not upload your image to the server, keeping the conversion private on your side.
PhotoKit

FreeConvert grants a generous upload limit (up to 1 GB) and removes the file after processing, making it convenient for large icons.
FreeConvert

GroupDocs provides both a free web app and a cloud-based API for ICO-to-BMP conversion, which is particularly useful if you're a developer automating conversion tasks.
GroupDocs Apps
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These tools typically work in the same basic way: you upload or drag your ICO file into the interface, choose BMP as the output format, optionally adjust settings, and then download the resulting BMP(s).

How to Convert ICO to BMP Locally (Software)
If you prefer not to rely on online tools, there are desktop applications and libraries that let you convert ICO to BMP:

IrfanView is a lightweight, fast image viewer and converter for Windows. With the appropriate plugins, IrfanView can open ICO files and save them as BMP.
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FormatFactory is a free multimedia converter that supports many image formats, including icons and bitmaps, making this conversion very straightforward.
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Icon Sushi is a specialized icon editor that can import ICO (or extract icons from EXE, DLL) and export to BMP.
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For developers, Conholdate.Total API supports Java-based ICO-to-BMP conversion, giving you programmatic control over resolution, quality, and batch operations.
products.conholdate.com

Cross-platform editors like LazPaint may also help, depending on their support for ICO import and BMP export.
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Technical Considerations
When converting ICO to BMP, it's important to keep in mind how ICO stores image data. As per the ICO file specification, each image inside an ICO may use BMP format internally, but with some differences in structure.
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Specifically, BMP data in ICO files excludes the standard BITMAPFILEHEADER, and often the height in the header is doubled to account for a mask (used for transparency).
Wikipedia
That mask is typically a 1-bit alpha mask, used to represent which pixels should be transparent. After conversion, some of that transparency information can be lost or flattened, depending on how the converter handles masks.

If your ICO contains multiple sizes, a converter may choose to output each size as a separate BMP file. High-resolution BMPs will naturally be larger in file size, especially if uncompressed. Also, because BMP is usually uncompressed, the final BMP files can take significantly more space than the ICO—even if the ICO included PNG-compressed images.

Quality and File Size Trade‑offs
Converting ICO to BMP often involves a trade-off between quality, size, and file structure. Because BMP is less compressed (in many cases), the resulting files might be much larger. But the advantage is that you preserve all the raw pixel data without any lossy compression. If you only need a specific resolution from your ICO (for example, just the 256×256 image), you can use a converter that lets you pick that size and ignore the rest, minimizing output size.

On the other hand, transparency handling can be tricky. Some converters will merge the transparency mask with the image so that transparent areas become solid (often white or black), while more advanced tools may preserve or simulate the mask in a way that's meaningful for your use case. It’s important to preview the converted BMP to make sure it meets your expectations, especially if you need transparent regions.

Security and Privacy
When using online ICO-to-BMP converters, remember that uploading images to a third-party service may have privacy implications. Reputable sites (like those mentioned above) often delete uploaded files after a short period, but it's wise to check their data retention policies. Using a browser-based converter that runs in your local browser (without uploading to a server) is one of the safest options for sensitive images. For automated or large-scale tasks, a local tool or a developer API may be more secure and efficient.

Use Cases for ICO to BMP Conversion
There are many real-world scenarios where converting ICO to BMP can be very useful. Designers may want to extract the icon images to edit them in a paint program or include them in documentation. Developers may need to render or manipulate icon graphics inside applications that only support BMP. Some game or UI engines may require BMP for textures or legacy support. Even when creating icon previews or exporting for legacy systems, BMP provides a simple, portable way to store pixel-perfect data.

Conclusion
Converting an ICO file to BMP format is a common task when you need to extract or flatten icon imagery for broader use. Thanks to modern converters—whether online tools, desktop programs, or APIs—this process is straightforward and flexible. Understanding the structure of ICO files, the trade‑offs between file size and quality, and the ways transparency is handled can help you choose the right method for your needs. Whether you’re a designer, developer, or just someone tinkering with icons, converting ICO to BMP expands how and where those icon images can be used.