How to Convert PNG, JPG, or BMP Images to ICO in Windows

To convert a PNG, JPG, or BMP image into a Windows icon, open it in GIMP and export it with the .ico extension. GIMP includes a Windows Icon export dialog where you can select several icon sizes and choose an alpha-capable pixel format. That gives Windows a choice of image sizes instead of asking it to enlarge or shrink one tiny bitmap.

Why an ICO file can contain several sizes

A Windows icon is commonly a set of square images stored in one .ico file. Microsoft lists 16 × 16, 32 × 32, 48 × 48, and 256 × 256 pixels as typical sizes. Windows can select the closest image for the place where the icon appears, which helps it stay clear in different views. A single-size file may look sharp at one scale and blurry at another. See Microsoft’s Windows icon guidance for the format and common sizes.

Before converting, simplify the artwork if it contains small text or fine details. Those details can disappear in a 16-pixel image; Microsoft recommends adjusting an icon’s detail for smaller sizes instead of relying on a simple reduction. A PNG can retain transparent edges. JPEG does not store transparency, and BMP files may be opaque, so use a PNG source when you need a transparent background.

Convert an image to ICO with GIMP

1. Install GIMP and open the source image. Get the Windows installer from the official GIMP downloads page. Start GIMP, choose File > Open, and select the PNG, JPG, or BMP you want to convert. If you have not installed GIMP, use the official download rather than an unofficial installer.

2. Make the artwork square when needed. Windows icons are square. If the image is not square, select the Crop tool and, in Tool Options, enable Fixed with an aspect ratio of 1:1. Drag the square around the subject and press Enter. Keep the subject centered and leave a little breathing room at the edges. If you need to preserve a wide image without cropping, place it on a square canvas instead; use transparency for a PNG or a solid background for an opaque image. GIMP’s Crop tool manual explains fixed aspect ratios.

3. Choose the ICO export format. Select File > Export As, enter a name such as custom.ico, and choose Export. GIMP uses Export for formats such as ICO; its native Save command is for GIMP project files. In the file dialog, confirm the type is Microsoft Windows icon (*.ico) if a format selector is shown.

4. Select icon sizes and transparency. In the Windows Icon export dialog, include 16 × 16, 32 × 32, 48 × 48, and 256 × 256 for a general Windows icon. Choose 32 bpp, 8-bit alpha if the image needs smooth transparency; GIMP’s manual identifies this as the common RGB-with-alpha format. For the widest compatibility, leave Compressed (PNG) off unless the software that will use the icon supports PNG-compressed ICO images. Click Export to finish.

Use the new icon in Windows

Keep the .ico file in a location that will not change. For a folder that offers the customization tab, right-click it, choose Properties > Customize > Change Icon > Browse, select the ICO file, and apply the change. A shortcut can also use a custom icon through its Properties dialog. These controls vary by Windows version and by the kind of item you are customizing.

There is a current Windows caveat for folder icons: Microsoft says security updates released on or after June 9, 2026 can cause Windows to ignore some custom folder icons supplied through desktop.ini when the file comes from an untrusted source or carries Mark of the Web. If a converted ICO works in an app but not for a downloaded folder, read Microsoft’s current custom-folder-icon notice. Only change trust settings or unblock files you know are safe.

If the icon does not look right

• The image is clipped: return to GIMP and adjust the 1:1 crop so the subject has more space around it. For a photo, choose whether a centered crop or colored padding better suits the image.
• The icon looks blurry at small sizes: simplify fine lines and text, increase contrast, and keep the most recognizable shape prominent. Check the design at 16 × 16 as well as 256 × 256.
• Transparency became a solid block: start with a PNG that already has transparent pixels and choose the 32 bpp, 8-bit alpha format in the export dialog. A JPEG cannot carry a transparent background.
• The file is not recognized as an icon: confirm the name ends in .ico and that GIMP exported it as Microsoft Windows Icon, not PNG with a renamed extension.

After those checks, export again and test the file in the Windows icon picker or the application that needs it. The useful result is one ICO file with the sizes and transparency your target supports.