BMP stores every pixel uncompressed. Converting usually cuts the file by 90% or more.
A BMP has essentially no compression, which is why a screenshot can be 6 MB. Converting to JPG, PNG or WebP keeps the picture and drops the bulk. It runs entirely in your browser.
Drag, drop or paste · BMP · no size limit
Converts BMP to JPG, PNG or WebP in your browser. The size comparison under the result is measured from your actual file, not estimated.
BMP stores pixels raw. A 1920 by 1080 image at 24 bits per pixel occupies about 6.2 MB no matter what the picture contains, because there is no compression step deciding that a plain blue sky can be described more briefly.
That is not a flaw, it was the point. BMP was designed so Windows could read an image straight into memory without decoding it. On hardware from 1990 that mattered. On anything since, the storage cost dwarfs the saving.
JPG typically lands between 3% and 10% of the original for a photograph. The compression is lossy, so fine detail softens slightly, but at quality 90 and above it is rarely visible.
PNG is lossless, so nothing is discarded, and it still usually cuts a BMP by half or more. For screenshots, diagrams and anything with flat colour and sharp text, PNG is the better choice, and often smaller than JPG as well.
WebP beats both on size in most cases and keeps transparency, at the cost of not being readable by some older desktop software.
Most BMPs in the wild are screenshots, and screenshots are the one case where JPG is usually the wrong answer. JPG compression works on gradual tonal change and struggles with hard edges, so text picks up a visible halo.
For anything containing text or interface elements, convert to PNG. It is lossless, it handles flat colour extremely well, and the result is normally smaller than the JPG would be anyway.
Keep going without re-uploading — your image carries over to the next tool automatically.