Convert PNG to BMP

Nobody picks BMP for its size. People need it because something downstream insists: an embroidery or laser-engraving program, a label printer driver, a game mod tool, a BIOS or boot-logo utility, a microcontroller display library, or a line-of-business Windows app written twenty years ago. Most of those expect the most basic variant, an uncompressed 24-bit bitmap, and that is exactly what this page writes.

BMP has no alpha channel in that variant, so transparent parts of your PNG are painted with the background colour you choose in the options. Pick white for printing and engraving, black for dark-background displays, or the exact colour your target software uses behind the image. The width and height stay the same as the PNG.

Expect a much larger file: the bitmap stores three bytes per pixel with no compression, so a 1000 by 1000 PNG becomes a 3 MB BMP however simple it looks. The conversion happens in your browser, and the PNG never leaves your device.

A few targets have their own quirks. Windows boot-logo and BIOS tools typically want a specific size, such as 640 by 480 or the exact screen resolution, so resize the PNG before converting. Embroidery software reads the bitmap as a colour map, so fewer colours make cleaner stitch regions. Arduino and ESP32 display libraries often read a 24-bit BMP from an SD card, row by row, which is precisely the bottom-up layout written here.

Colour depth is the setting people most often get wrong. A PNG exported from a design tool is usually 32-bit, with an alpha channel. Many BMP readers in embedded and legacy software handle only 24-bit and either refuse a 32-bit bitmap or draw its transparent pixels as black. Writing 24-bit with the transparency flattened onto a colour you picked avoids both problems.

If your software refuses the file, check what it expects before trying again: some programs want the .bmp extension in capitals, a maximum size, or an 8-bit palette. Those are rare, and the 24-bit output from this page is what almost every BMP reader is built to accept.