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How to make an ICO file from a PNG that doesn't look blurry: multi-size icons for Windows

By Marduk Syndicate Updated 16 Sep 2026 Limits last verified 16 Sep 2026

Most online ‘PNG to ICO’ tools give you one size, and Windows then stretches it. The fix is an ICO that contains several sizes, which is what Windows expects. Here’s which sizes, with a test, and the one-click way to make one.

Why a single-size ICO looks blurry

An .ico file is a container that can hold several images at different sizes. When Windows needs to draw an icon, Microsoft’s documentation says it “will look for an exact size match first. If there is no exact match it will look for the next size above and scale down.” If the only image in the file is 32 × 32 and Explorer wants 48 or 256, it scales the 32 up, and you get a soft, blocky icon.

Microsoft’s minimum recommendation is clear: “Apps should have, at the bare minimum: 16x16, 24x24, 32x32, 48x48, and 256x256.” The 256 is what large-icon and thumbnail views use; the small ones are for the title bar, context menus, the taskbar and the tray.

Source: Microsoft Learn, Construct your Windows app’s icon, checked 16 Sep 2026.

The test

We took a 256 × 256 PNG and built two ICO files on 16 Sep 2026: one containing 256, 48, 32, 24 and 16 px, and one containing only 32 px.

FileSizes insideFile size
multi.ico256, 48, 32, 24, 16288 KB
single32.ico324.3 KB

Here’s what Windows would have to do with the single-size file when it needs a 256-px icon, next to the real 256-px image:

32 px stretched to 256
A small app icon scaled up from 32 to 256 pixels: the edges are blocky and the shapes have lost their curves
Real 256 px
The same icon rendered from a real 256-pixel image: crisp edges and smooth curves
Left: the 32-px image scaled up to 256, which is what a single-size ICO gives you in large-icon views. Right: the 256-px image a multi-size ICO carries.

The 288 KB is almost all the 256-px image; the four small sizes add under 20 KB.

Making one

In Simple Image Converter: drop the PNG (or SVG), click the Make icon (ICO) preset, Convert All. It writes a multi-resolution ICO with sizes from 16 to 256 px in one file, and it does a folder of logos in one batch. Start from a square image of at least 256 × 256, ideally with a transparent background; Microsoft notes icons “look best with a transparent background”.

Simple Image Converter · Make icon
Simple Image Converter converting an app logo PNG, a badge, a favicon source and an SVG mark to ICO, with ICO selected as the output format
Four sources, including an SVG, converting to multi-size ICO files in one batch.

Using the ICO on Windows

  • A folder: right-click the folder → Properties → Customize → Change Icon… → Browse to the .ico. Windows writes a desktop.ini in the folder to remember it.
  • A shortcut: right-click the shortcut → Properties → Shortcut → Change Icon… → Browse.
  • A drive: an autorun.inf with an icon= line on the drive’s root, which Windows honours for most removable drives.

Keep the .ico somewhere it won’t move (not Downloads), because Windows stores the path, not the file. Simple Image Converter is a one-time purchase on Steam, for Windows and SteamOS/Linux.

Get Simple Image Converter on Steam