WebP to BMP Converter

BMP is the plain Windows bitmap: no compression, no clever encoding, so almost any program can read it — old Windows software, embedded devices, label printers, game engines and some industrial tools that refuse WebP. This converter decodes each WebP with your browser and writes a standard BMP. Choose 24-bit colour for the widest compatibility, 32-bit to keep transparency, or 8-bit greyscale for the smallest bitmap.

How to use this tool

1. Drop one or more .webp files.
2. Pick the BMP type: 24-bit, 32-bit with transparency or 8-bit greyscale.
3. For 24/8-bit choose the colour that replaces transparent areas, and optionally the stored DPI or a max size.
4. Download each BMP, or all of them as a ZIP.

Formula

BMP size = 14 (file header) + 40 (info header; 108 for 32-bit) [+ 1,024 for the 8-bit palette] + height × row, where row = width × bytes per pixel rounded up to a multiple of 4.

Rows are stored bottom-up in blue-green-red order. 32-bit files use a BITMAPV4HEADER with bit masks that include an alpha channel, the standard way to store transparency in a BMP. 8-bit files use a 256-step grey palette made with the Rec. 601 luma weights (0.299 R + 0.587 G + 0.114 B). DPI is stored as pixels per metre.

Example

A 160 × 100 px WebP becomes a 24-bit BMP of exactly 14 + 40 + 100 × 480 = 48,054 bytes, a 32-bit BMP of 14 + 108 + 100 × 640 = 64,122 bytes, or an 8-bit greyscale BMP of 14 + 40 + 1,024 + 100 × 160 = 17,078 bytes. A WebP of a few kilobytes can therefore become a much larger bitmap.