BMP → ICO Converter

Drag & Drop your .bmp here, or pick a file below. Nothing is uploaded.

Tip: Square images work best for icons. Non-square inputs are letterboxed/padded if needed.

Icon sizes to include

Including 256x256 (PNG-compressed) is recommended for high-DPI.

Canvas fit

Pad to square (letterbox if needed)

Force opaque (fill background)

Load a BMP or use an example to preview.

Input: -

ICO frames: -

BMP → ICO - Quick Cheat Sheet

Local only: Everything happens in your browser; your file is not uploaded.
PNG vs BMP inside ICO: This tool embeds PNG-compressed frames for best quality/size (supported by modern Windows and browsers). Very old tools (XP-era) may need legacy BMP-style ICOs.
Sizes: Include at least 16, 32, 48, and 256 px for good coverage. More sizes make the ICO bigger.
Transparency: If your BMP has no alpha, enable "Force opaque" and choose a background color.
Square fit: Non-square inputs are letterboxed into a square canvas to avoid distortion.
Favicon tip: ICO is still the most compatible favicon format. Also serve PNGs for modern browsers if you like.

How the ICO is built

Each selected size is rendered on a square canvas, optionally padded or filled.
Frames are individually PNG-encoded, then packed into a single ICO using a standard ICONDIR + ICONDIRENTRY table.
Byte fields for width/height use 0 to mean 256, per the ICO spec.