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Need help?ICO to ICO: Resizing an Icon That Is Already an Icon
An .ico is not a single picture — it is a small directory of images, each with its own dimensions, that Windows and browsers pick from depending on where the icon is drawn. Converting ICO to ICO re-renders that content on our servers at one size you choose. That is worth doing when an icon is the wrong dimensions for the slot it has to fill, when a 256-pixel icon is far heavier than a favicon needs to be, or when a file needs rewriting into plain, ordinary ICO bytes. It is worth understanding first, because the single control on this page sets a height, and an icon directory has strong opinions about width.
How to Convert ICO to ICO
- Upload Your ICO File: Drag and drop the
.icoonto the page or click "+ Add Files". Only.icofiles are accepted here, and you can queue several — they all take the same preset. - Pick a Preset Resolution: "Image resolution" offers a single "Preset Resolutions" list — 256P, 192P, 180P, 128P, 64P, 48P, 32P, 24P and 16P. Nothing else on the panel applies to an ICO target, so this one choice is the whole conversion. Pick the size the icon actually has to be drawn at.
- Match the Preset to Your Icon's Shape: The preset sets the output height and the width follows your image's aspect ratio. A square icon is safe at every preset. A non-square one is only safe while the resulting width stays at or below 256 — see the table below before choosing anything above 128P.
- Convert and Download: Click "Convert" and take the
.ico. No sign-up, no watermark.
The Preset Sets Height — Here Is What That Means
An icon directory entry stores its width and height in one byte each, and a zero is the special value meaning 256. Nothing larger can be described. Because the preset controls only the height, a wide source can be scaled to a width that will not fit in that byte, and the entry ends up declaring the wrong number.
Measured on ImageMagick 7.1.2 — the build that runs this conversion — across three source shapes:
| Preset | Square source | 4:3 source | 16:9 source |
|---|---|---|---|
| 256P | 256 x 256, correct | 341 x 256, declared 256 x 256 | 455 x 256, declared 256 x 256 |
| 192P | 192 x 192, correct | 256 x 192, correct | 341 x 192, declared 85 x 192 |
| 180P | 180 x 180, correct | 240 x 180, correct | 320 x 180, declared 64 x 180 |
| 128P | 128 x 128, correct | 171 x 128, correct | 228 x 128, correct |
| 64P and below | correct | correct | correct |
The pattern is arithmetic, not randomness: the declared width is the real width wrapped to a single byte, so 320 is written as 64 and 341 as 85. At 256P the encoder switches to an embedded-PNG entry and writes zeroes in both fields, which is legal shorthand for 256 x 256 — accurate for a square icon, and a plain misstatement for a wide one. Treat 128P as the ceiling for a 16:9 icon and 192P for a 4:3 one. Square icons — which is what most .ico files hold — are unaffected at every preset.
What Happens to a Multi-Size Icon
This is the other thing to check before converting. A favicon-style .ico usually contains a ladder of sizes: 256, 128, 64, 48, 32 and 16 pixels, so the operating system can pick the right one. Every one of those entries is read, scaled to the preset you chose, and written back out.
| Input | Output at the 128P preset | File size |
|---|---|---|
| Single 48 x 48 entry | One 128 x 128 entry | 67,646 B |
| Six entries (256/128/64/48/32/16) | Six entries, all 128 x 128 | 405,846 B |
The six-entry file comes back six times heavier carrying six copies of the same picture, and the size ladder — the entire reason the icon had several entries — is gone. If your source is a multi-size icon and you want a small single-size one, that is exactly what this page produces, just at six times the necessary weight; if you wanted to keep the ladder, do not convert it here. To build a fresh icon from artwork at a chosen size, start from the image instead with PNG to ICO.
Frequently Asked Questions
Why is there only one setting on this page?
Because ICO has almost nothing to tune. There is no quality slider, no bit-depth choice and no palette control on an ICO target — the format stores a bitmap (or an embedded PNG) and a directory entry describing it, so the only meaningful decision is how big that bitmap should be. The controls you may have seen on other image pages are hidden here rather than being ignored: the panel genuinely offers the preset list and nothing else.
What size is selected when I do not touch the preset?
The list opens on 256P, its first entry. The stored default for this control is a value that does not exist in the ICO list, so the interface falls through to the top of the list rather than to something sensible. On a square icon 256P is fine — it is the largest size the format defines. On a wide or tall one it is the least safe choice, so pick explicitly rather than accepting what the dropdown shows.
Why did my icon come out rectangular instead of square?
Because the preset sets the height and the width follows the source's aspect ratio — nothing is cropped or padded to a square. An .ico is allowed to hold a non-square image, so a 16:9 source at the 128P preset legitimately produces a 228 x 128 icon. If you need a square result from a non-square source, crop it to a square before converting; there is no cropping or padding option on this page.
Can I build a multi-size favicon with all the standard sizes here?
No. Each conversion writes one size, and if the source contained several entries they all end up at that same size. A proper favicon ladder is built by generating each size separately and assembling them, which this page does not do. What it is good for is producing one clean, correctly sized icon — for example taking an oversized 256-pixel .ico down to the 32P or 16P that a browser tab actually draws.
Why is my converted icon so much larger than the original?
Almost certainly because the source held several sizes. Every entry in the input is scaled to your chosen preset and written out, so a six-entry icon becomes six same-sized entries — we measured 405,846 bytes from a six-entry source versus 67,646 bytes from a single-entry one at the same preset. The fix is to convert from a source with one image in it, or to start from a plain image with PNG to ICO.
Does transparency survive the conversion?
Yes. We converted an icon whose background was fully transparent and whose foreground was an opaque circle; in the output the background pixels were still fully transparent and the foreground kept its colour exactly. ICO stores an alpha channel, so a rounded or cut-out icon keeps its shape rather than gaining a white or black box.
What is the largest icon ICO can hold?
256 x 256 pixels. That limit is baked into the directory structure — the width and height fields are one byte each, with zero used as shorthand for 256 — which is why the preset list stops at 256P and why anything scaled past 256 pixels wide cannot be described honestly. If you need artwork bigger than that, ICO is the wrong container; keep the source image and export the icon separately.
Will scaling a small icon up to 256P make it sharper?
No, and it usually looks worse. If the entry that gets read is a 16 or 48 pixel image, a 256P preset stretches those few pixels across a much larger canvas and the result is soft and blocky — there is no detail to recover. Scale up only when something downstream demands a specific larger size, and go back to the original artwork if you have it. Converting downward, from a large entry to a small preset, is where this page produces genuinely good results.
How are my files handled, and how long do you keep them?
Your icon is uploaded over an encrypted connection, re-rendered on our servers, and deleted automatically a few hours after conversion — no sign-up, no watermark, never shared or made public. Icons are tiny by the standards of this site, so conversion is quick. If you would rather have the artwork as an ordinary picture you can open and edit anywhere, ICO to PNG renders the icon's first stored image as a PNG.