What a BMP file is
BMP, short for bitmap, is one of the oldest image formats. It stores pixels almost as they are, with a small header and then the color values row by row. There is no compression, which makes the format simple to read for old software, embedded devices and some industrial or scientific tools, but it also makes files large.
This tool writes a 24-bit BMP, meaning three bytes per pixel: blue, green and red. Rows are stored from the bottom of the picture upward, and each row is padded so its length is a multiple of four bytes. These are standard BMP rules, and most programs open the result without trouble.
A quick size example: a 100 by 100 pixel image needs 300 bytes per row (100 pixels times 3 bytes, already a multiple of four), so 30,000 bytes of pixel data plus a 54-byte header, for a file of 30,054 bytes.
When you actually need BMP
Most people never need it, since JPG and PNG cover everyday use. BMP matters when a program or device specifically asks for it, such as legacy Windows software, boot screens and splash images, some label printers, and older game or hardware tools.
Because the file is uncompressed, size depends only on the pixel dimensions. A 1920 by 1080 image comes to 6,220,854 bytes, roughly 6.2 MB, no matter whether the picture is a photo or a blank page. If you want a smaller lossless file for normal use, try JPG to PNG or the general image format converter instead.
How to convert an image to BMP
- Drag an image onto the upload area, or click to select one. Any image format your browser can display is accepted.
- A preview of your image appears.
- If the image has transparent areas, pick the background color that should show through. It is white by default. BMP cannot store transparency, so those areas are filled with this color.
- Click Convert to BMP. When it finishes, a Download button appears next to it. Click it to save the file, which keeps your original name with a .bmp extension.
- Use Start over to load a different image.
The conversion runs entirely in your browser by reading the pixels from a canvas, so the image is not uploaded anywhere. The tool does not show a preview of the BMP result or its file size, so check the downloaded file on your device if you need the exact size.
Limits and things to watch for
The output is 24-bit with no alpha channel, so transparency is not preserved. Transparent areas are painted with the background color you chose (white unless you change it), and partly transparent edges blend into that color.
The original pixel dimensions are kept, with no resizing or color depth choice. Very large images create very large BMP files and need enough memory in the browser, so scale a big photo down with the image resizer first if it is not required at full size.
Many web uploads reject BMP or convert it anyway, so check what the destination actually requires before choosing it.