JPG to ICO Converter

Windows icons, desktop shortcuts and old-style favicons use the ICO format, a small container holding the same picture at several sizes. Photos and logos usually arrive as JPG, which is rectangular and has no transparency, so the picture first has to be made square. This tool crops or pads it, draws it sharply at every size you tick and writes a real multi-image .ico — in your browser, without uploading anything.

How to use this tool

1. Choose one or more JPG images — ideally square and at least 256 × 256 px.
2. Tick the sizes the icon should contain (16, 32, 48 and 256 cover Windows Explorer, the taskbar and shortcuts).
3. Pick how to make it square: crop the centre, crop from the top for portraits, or fit inside with transparent or white padding.
4. Download the .ico file and check the list of images inside it.

Formula

ICO = ICONDIR (6 bytes: 0, type 1, image count) + one 16-byte ICONDIRENTRY per size (width and height — 0 means 256 — planes 1, 32 bits per pixel, byte length, offset) + the image data, each size stored as a PNG.

Cropping uses the largest square that fits: min(width, height) on each side, taken from the centre or from the top edge. Big reductions are done in halving steps with high-quality smoothing, so small sizes stay crisp. The classic option stores 48 px and smaller as 32-bit BMP data with a transparency mask, which Windows XP and some older programs need.

Example

A 1200 × 800 px JPG logo with "Crop to a square — centre" uses the middle 800 × 800 px (x from 200 to 1000). With the default sizes the .ico holds four images, 16, 32, 48 and 256 px. With "Fit inside, transparent padding", the 256 px image instead shows the whole logo at 256 × 171 px with transparent bands of 42 px above and 43 px below.