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BMP to ICO Converter

BMP is uncompressed — files are enormous for no visual benefit. Converting to Windows ICO icons gives you the icon format browsers look for at /favicon.ico and Windows uses for shortcuts. The size is the entire issue — email attachment limits, upload caps and disk space all bite long before quality does. Common BMP variants also carry no alpha channel, so there is no transparency to lose, and none to gain by staying put. Website favicons and Windows shortcut icons — a square source with clear shapes that still read at 16 pixels. Drop your files below and the work happens on your own machine: the conversion runs in the browser through the Canvas API, so nothing is uploaded, there is no file-size cap, no watermark and no sign-up. Batches are fine — drop a folder's worth and take them back as a single ZIP.

Drop images here

or click to browse — JPG, PNG, WebP, HEIC, AVIF, GIF, BMP, SVG

Private: files never leave your device

What a BMP file actually is

BMP is Microsoft's original raster format and in normal use stores pixels with no compression at all: three bytes per pixel, plus a header. A 12-megapixel photo lands around 36 MB. An optional run-length mode exists but is rarely produced.

BMPs turn up from legacy Windows software, older scanner drivers, industrial and medical equipment, and Paint on an ancient machine. New files in this format are almost always a sign that something in the chain has not been updated in a long time.

What you get from ICO

ICO is a container that holds one or more small square images, with transparency, for use as an icon. It caps out at 256×256 — anything larger has to be scaled down, and the format is not intended for general pictures.

Every browser requests /favicon.ico by default, with no HTML required, and Windows uses ICO for application and shortcut icons. It is a narrow format that is completely reliable inside its niche.

What changes when you convert BMP to ICO

Both formats are lossless, so nothing is thrown away in either direction — this is a container change rather than a quality decision. What differs is how efficiently each one packs the same pixels, and how widely each is supported by the software you need to open it in.

There is no transparency to preserve — BMP files do not carry an alpha channel, so every pixel is opaque to begin with. Converting to a format that supports transparency does not create any; it only means you could add it later in an editor.

ICO cannot exceed 256×256, so anything larger is scaled down to fit while keeping its aspect ratio. Work from a square source if you can — a wide image gets letterboxed into the square, and fine detail disappears entirely at the 16-pixel size a browser tab actually renders.

Size stops being the interesting question here, because the image is being scaled to at most 256×256 regardless. What matters is that a BMP from an old Windows tool is often already small and square, which makes it an unusually good icon source — the pixels are unprocessed and there is no prior compression to fight.

Frequently asked questions

Is this BMP to ICO converter really free and private?

Yes. Conversion happens entirely in your browser using the Canvas API — your BMP bitmaps are never uploaded to a server, there is no file limit, no watermark and no sign-up.

Can I convert multiple BMP files at once?

Yes — drop any number of files and they convert in one batch. Use "Download all" to save the results as a single ZIP.

What size will my ICO file be?

ICO cannot store an image larger than 256×256, so anything bigger is scaled down to fit while keeping its aspect ratio. For a browser favicon a square source works best — 256×256 covers every modern use, and browsers scale it down to the 16 or 32 pixel tab icon themselves.

How do I use this as my website favicon?

Save the file as favicon.ico in your site's root directory. Browsers request /favicon.ico automatically, so no HTML is strictly needed — though adding <link rel="icon" href="/favicon.ico"> makes it explicit.

Does converting BMP to ICO lose quality?

Both formats are lossless, so nothing is thrown away in either direction — this is a container change rather than a quality decision. What differs is how efficiently each one packs the same pixels, and how widely each is supported by the software you need to open it in.

Should the icon be square?

Yes. ICO holds square images, so a wide or tall source is fitted into the square and ends up with empty space around it. Start from a square design with generous margins — the tab icon renders at 16 pixels, where anything intricate turns to mush.

Will I lose anything by leaving BMP behind?

Effectively nothing. BMP stores raw pixels with no compression and, in its common variants, no transparency — so there is no quality advantage to preserve. The conversion is close to pure size saving.

Related conversions

JPG → ICOPNG → ICOWebP → ICOHEIC → ICOAVIF → ICOGIF → ICO

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