Convert image to BMP

1. Drop your images onto “Drop images here”, click to choose them, or paste from the clipboard. You can load several at once.
2. Check that BMP is selected under “Convert to”; on this page it comes preselected.
3. Under “Bit depth”, choose “24-bit” (no transparency) or “32-bit” (with alpha). 32-bit is selected by default.
4. If you need different dimensions, open “Resize” and choose “Dimensions” to enter the “Width” and “Height”, or “Scale” to shrink or enlarge proportionally.
5. Press “Convert to BMP”. Under “Converted”, download each file with “Download”, or all of them together with “Download all as ZIP” if you converted several. Each file keeps its name with a .bmp extension.

BMP is the Windows bitmap format. It stores pixels one by one, uncompressed, behind a simple header. That is why old programs, some industrial machines and electronics projects that have no way to decompress a PNG or JPG can read it.

For the web, for sending photos or for archiving them it has no advantages: a PNG stores the same pixels without losing quality and takes up less space. Use BMP when a program or device asks for it.

The file starts with a 54-byte header: 14 bytes of file header and 40 of image information (BITMAPINFOHEADER). The uncompressed pixels follow, top to bottom, in blue, green, red order. At 24-bit each pixel takes 3 bytes; at 32-bit it takes 4, because the alpha channel is added.

Each row is padded with zeros to a multiple of 4 bytes, as the format requires. So you can work out the size before converting: width × height × 3 bytes at 24-bit (or × 4 at 32-bit), plus that padding and the header. The resolution written into the file is 72 dpi; it only matters if the program uses it for printing.

At 24-bit there is no alpha channel, so transparent areas in a PNG, WEBP or SVG are filled with white before saving. At 32-bit the transparency of each pixel is kept, but not every program reads it: if yours does not display those areas properly, convert again at 24-bit.

The tool accepts any image your browser can open, including SVG. An SVG is turned into pixels before saving; if it does not state its size, a small one is given 1024 pixels on the long side. For another size, set it under “Resize”.