BMP is raw uncompressed pixels, which is why the files are so large. JPEG is lossy compression tuned for human vision, and no alpha channel at all. ImageMagick sits between the two, and this page says exactly what happens to a BMP file on the way to becoming a JPG one.
What runs when a BMP file becomes JPG
ImageMagick 6.9.12, on a machine we rent and watch. Your BMP file is uploaded once, ImageMagick runs once, the JPG comes back, and neither file is kept. BMP to JPG is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the BMP into the JPG
The pixel dimensions of your BMP file. The JPG comes out the size the BMP went in, because nothing on this path resizes anything.
What BMP to JPG costs you
Exactness. JPG is a lossy encoding, so the file you get back approximates the BMP you sent. The artefacts appear once and never come out again, which is why converting the JPG back to BMP afterwards restores nothing.
If a model is going to read the JPG
A JPG file is pixels, and pixels are expensive for a model to read. Handed this JPG, an assistant spends its budget looking at the picture rather than reading it, and it will paraphrase what it thinks it saw. If your BMP is mostly words, the useful move is to pull the text out of it, not to change which picture format holds it.
BMP to JPG, measured rather than promised
Running BMP to JPG against the real engine with a real file, ImageMagick wrote 1,568 bytes of JPG in under a tenth of a second, machine otherwise idle. That is one BMP file on one day and not an average, which is why the number is given together with the file that produced it.
The BMP to JPG verdict was reached by a format signature, meaning at least four bytes unique to the format were found at the right offset. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the JPG file has anything inside it.
The same BMP file, sent somewhere else
Other outputs the probe measured out of a BMP file, so the cost of choosing JPG can be read against something. Sizes do not compare across engines, because each family was probed with its own BMP witness file.
BMP to PDF: 118,745 bytes in under a tenth of a second, verified by a format signature.
BMP to PNG: 810 bytes in under a tenth of a second, verified by a format signature.
BMP to WEBP: 370 bytes in under a tenth of a second, verified by a format signature.
BMP to GIF: 3,799 bytes in 0.1 seconds, verified by a format signature.
BMP to TIFF: 72,264 bytes in under a tenth of a second, verified by a format signature.
Other ways into JPG, and what they measured
Among the published routes into JPG, BMP is the ninth largest output of the 13 measured. The witness files differ, so this ranks the probe run and not your document.
TIFF to JPG: 1,568 bytes in under a tenth of a second.
AVIF to JPG: 1,705 bytes in under a tenth of a second.
SVG to JPG: 2,483 bytes in under a tenth of a second.
PSD to JPG: 1,568 bytes in under a tenth of a second.
ICO to JPG: 1,568 bytes in under a tenth of a second.
What we will not pretend about BMP to JPG
A BMP file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A BMP to JPG run that passes 30 seconds is killed, and the ImageMagick process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
No text is read out of the BMP anywhere on this path. Converting a picture to JPG never turns it into words, whatever the picture happens to contain.
ImageMagick was not saturated at sixteen simultaneous conversions: it held 47.5 a second while latency moved from 0.22 s to 0.34 s, and the service memory did not move off 51 MB. That is the measured headroom behind BMP to JPG, not a marketing number.
One BMP file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
BMP to JPG: what people ask
What actually converts my BMP file to JPG?
ImageMagick does it, 6.9.12, on a machine we rent and watch. Not a browser trick and not somebody else service: the BMP file is uploaded once, ImageMagick runs once, the JPG comes back, and neither file is kept afterwards.
How long does BMP to JPG take?
On the file the probe used, ImageMagick took under a tenth of a second and wrote 1,568 bytes of JPG. That is one real measurement on one real BMP file, not an average and not a promise about yours: a larger BMP takes longer, and past 30 seconds the run is stopped.
What do I lose going from BMP to JPG?
The one to know about first: Exactness. JPG is a lossy encoding, so the file you get back approximates the BMP you sent. The artefacts appear once and never come out again, which is why converting the JPG back to BMP afterwards restores nothing.
Will the JPG look worse than the BMP?
Slightly, and permanently. JPG is a lossy encoding: it discards detail on the way out and the file never gets it back, so converting the JPG to BMP again restores nothing. Keep the BMP if it is your only copy of the picture.
Is BMP to JPG free?
There is a free allowance every month, and one BMP to JPG conversion costs half a credit against it. When the allowance runs out the tool says so and stops, rather than quietly handing you a worse JPG.