Why is the BMP so much larger than the JPG?

BMP stores three bytes per pixel with no compression, while JPG throws away data and packs the rest. A small JPG can expand into a BMP many times its size because every pixel is written out in full.

Does converting to BMP recover detail the JPG lost?

No. JPG compression is lossy, so any detail it discarded is already gone. The BMP records exactly the pixels the decoder produced, including any compression artifacts that were baked in.

What bit depth does the BMP use?

Each file is written as a 24-bit BMP: eight bits each for red, green, and blue. The pixels are stored bottom-up with rows padded to a four-byte boundary, following the standard BITMAPINFOHEADER layout.

How is transparency handled?

A 24-bit BMP has no alpha channel. If a pixel is partly transparent after decoding, it is blended onto a white background, so the saved image is fully opaque.

Can I convert several JPGs at once?

Yes. Drop as many as you like; each is converted on its own and added to the list, and the Download all button packs them into a single zip.

Are my images uploaded anywhere?

No. Decoding and BMP encoding both run in your browser, so the files stay on your device.

JPG to BMP

Writes your JPG out as an uncompressed 24-bit BMP.

What this does

A JPG holds its pixels in a compressed, block-based form: the encoder discards detail the eye is unlikely to notice and packs what remains into a small file. A BMP does the opposite. It writes every pixel out in full, row by row, with no compression at all, so the same picture takes far more space but maps directly to the raw color values.

This tool decodes each JPG in your browser, paints it onto a canvas, and writes the result as a 24-bit BMP. BMP has no alpha channel, so any area that ended up transparent during decoding is flattened onto a white background. The work happens on your machine; the images are never sent to a server.

How it works

1Drop your JPG files, or click to pick them.
2Each one is decoded and re-saved as an uncompressed 24-bit BMP.
3Download a single BMP, or grab the whole batch as a zip.

Built on web standards

Built with standard browser APIs — no third-party libraries.

Frequently asked questions

Related tools

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