Convert JPG to BMP: Free Online Converter

JPG is the world's most popular photo format, using DCT-based lossy compression to shrink image files by discarding visual information the human eye is less sensitive to. BMP (Bitmap) is Microsoft's uncompressed raster format, dating back to Windows 3.0 in 1990, which stores raw pixel data with no compression by default. Converting JPG to BMP decodes the JPEG compression and writes every pixel value directly to disk, producing a much larger file that can be read instantly by any Windows application without a decoding step.

This conversion is most relevant when working with legacy Windows software, embedded systems, or hardware that requires raw pixel data input. The resulting BMP file preserves the exact pixel values from the decoded JPG: it cannot recover detail lost during JPEG compression, but it guarantees no further degradation will occur regardless of how many times the BMP is opened, edited, or resaved.

Certain Windows-based industrial systems, medical imaging viewers, and kiosk software only accept BMP files because they lack JPEG decoding libraries. These applications were written in the 1990s or early 2000s when processing power was limited, and reading raw BMP pixel data was significantly faster than performing DCT decompression on JPEGs. If you need to feed photographic images into such systems, converting JPG to BMP is the required step.

BMP is also the native clipboard format on Windows. When you paste an image from the clipboard, Windows uses BMP internally. Some screen capture and annotation tools export only BMP, and certain printing workflows expect BMP input for direct rasterization without codec dependencies. Additionally, game modding communities often require BMP textures for older game engines that predate PNG and JPEG support.

Sharp decodes the JPG file's DCT-compressed data back to raw RGB pixels, then writes them into a BMP file with a 54-byte BITMAPINFOHEADER followed by uncompressed 24-bit (3 bytes per pixel) row data, padded to 4-byte boundaries per row. A 1920x1080 JPG that might be 300 KB as JPEG becomes approximately 5.9 MB as 24-bit BMP. The conversion preserves the full 8-bit-per-channel color depth from the decoded JPEG.