BMP to JPG Converter

BMP stores images without compressing them

A Windows bitmap writes out three bytes for every single pixel and stops there. A 4000×3000 image is therefore about 36 MB regardless of what it depicts — a photograph and a blank white rectangle come out the same size. That is why BMP files feel absurdly large next to everything else on the disk, and why this is one of the most dramatic conversions available: the same picture as a JPG is routinely 95% smaller.

Where BMPs still come from

Mostly from machines and older software rather than from people. Scanners and multifunction printers default to BMP surprisingly often, industrial cameras and microscopes emit it, some Windows utilities still save it, and older medical and surveying equipment produces nothing else. If a BMP has landed in your hands, it is usually because a device put it there and the next system in the chain will not take it.

What you actually lose

BMP is lossless, JPEG is not, so this conversion does discard information. At quality 90 that difference is invisible for photographic content at normal viewing sizes. It is worth thinking about in two cases: if the image is a diagram, screenshot or scan of text with hard black-on-white edges, JPEG will put faint ringing around those edges — convert to PNG instead, which stays lossless and still shrinks the file substantially. And if this is a master copy that will be edited repeatedly, each save loses a little more, so keep the original.

Transparency and odd colour depths

Most BMPs have no alpha channel, so there is nothing to lose. The handful of 32-bit BMPs that do carry transparency will have it flattened onto white, because JPEG cannot store it. Very old 1-bit, 4-bit and 8-bit palette bitmaps decode and convert normally.

Nothing is uploaded

Your browser decodes the bitmap and re-encodes it on a canvas, entirely in this tab. Given that BMPs often arrive straight from a scanner and contain documents or medical images, that matters — nothing here is transmitted anywhere.

Common questions