BMP converter
Convert BMP files while handling large bitmaps, palettes, alpha masks, Windows DIB variants, and modern image targets.
.bmp
Format
About BMP
BMP is the Windows bitmap family built around a small file header followed by a Device Independent Bitmap header, optional palettes or masks, and raw pixel rows. The format is simple compared with PNG or AVIF, which is why old desktop software, firmware tools, test fixtures, and Windows utilities still produce it. That simplicity also explains the file size: many BMPs store pixels with little or no compression. Our image routes can turn BMP into PNG, JPG, WebP, ICO, PDF, TIFF, AVIF, HEIC, or GIF when those pairs are enabled, and they can also make BMP from common raster and vector sources for systems that still demand it.
There is not just one bitmap layout. Older BITMAPCOREHEADER files differ from the more common BITMAPINFOHEADER family, and later V4 or V5 headers can carry channel masks, color space fields, and alpha-related data. Rows are padded to four-byte boundaries, pixels are often stored bottom-up, and color channels commonly appear in BGR order rather than RGB. Indexed BMPs depend on palette entries, while 16-bit and 32-bit files may rely on bit masks. RLE compression exists but is uncommon in web workflows. These details are mundane until a decoder flips the image vertically, ignores alpha, or reads colors in the wrong order.
Readers and writers include Windows APIs, paint programs, scanners, embedded device utilities, games, icon authoring tools, and QA suites that prefer uncompressed test images. Browsers can decode many BMP files, but web publishing rarely wants BMP because file sizes are high and metadata support is thin. Design teams usually convert BMP screenshots to PNG. Photo-like BMPs are usually better as JPG, WebP, or AVIF. Icon workflows may turn a bitmap into ICO, but the source needs to be redrawn or resized carefully for tiny favicon sizes rather than blindly downsampled from a large screenshot.
BMP conversion problems are mostly about preserving exact pixels while moving to formats with different expectations. BMP to PNG is the safest modern still-image target when sharp edges or palettes matter. BMP to JPG reduces size for photographs but adds lossy artifacts and removes any transparency. BMP to ICO creates an icon container but does not invent a full size ladder unless the converter is told to. BMP to PDF embeds a raster page and depends on pixel dimensions and DPI assumptions. Before batch conversion, check bit depth, transparency, dimensions, and whether the receiver expects a Windows bitmap specifically or only wants a broadly readable image.
Common BMP problems
A BMP is too large for upload or email.
Use /convert/bmp-to-png for lossless compression or /convert/bmp-to-jpg for photo-like content after checking for artifacts.
A legacy app needs a bitmap, but the source is PNG.
Use /convert/png-to-bmp and test the result in that app because alpha and color masks may be interpreted differently.
Transparent pixels appear black after conversion.
Prefer /convert/bmp-to-png when alpha matters, or flatten intentionally before /convert/bmp-to-jpg.
A favicon made from a large bitmap looks muddy.
Use /convert/bmp-to-ico, then inspect small sizes and redraw details that disappear at 16 or 32 pixels.
A scanned bitmap needs a shareable document wrapper.
Use /convert/bmp-to-pdf when a raster page is acceptable, and keep the BMP if exact source pixels are evidence.