BMP (Bitmap) is one of the oldest image formats, developed by Microsoft for Windows in the late 1980s. It stores pixel color data with little or no compression, which makes BMP files extremely large compared to JPEG, PNG, or WebP. Today BMP is rarely used for sharing or web use — but you may still encounter it in older Windows applications, some printers, and certain graphics software.

What BMP Stores

A BMP file stores pixel data in a simple grid format: each pixel gets its own color value, row by row from the bottom-left to the top-right. The file includes a small header (the file size, dimensions, color depth) and then the raw pixel data. Most BMPs are completely uncompressed — every pixel is stored regardless of whether it matches the surrounding pixels.

Color depths supported: 1-bit (monochrome), 4-bit (16 colors), 8-bit (256 colors), 16-bit, 24-bit (16.7 million colors), and 32-bit (with alpha channel)
No lossy compression: BMP preserves every pixel exactly. A 1000×1000 pixel 24-bit BMP is exactly 3 MB (1,000 × 1,000 × 3 bytes)
Optional RLE compression: BMP supports Run-Length Encoding (RLE) for 4-bit and 8-bit images, but it is rarely used and provides only modest compression

How Large Are BMP Files?

BMP files are much larger than compressed formats:

A 1920×1080 24-bit BMP = approximately 6 MB
The same image as JPEG at 85% quality = approximately 300–600 KB (10–20× smaller)
The same image as PNG = approximately 1–2 MB (3–6× smaller)
The same image as WebP = approximately 150–400 KB (15–40× smaller)

For web use, email, or any sharing scenario, BMP is almost always the wrong choice.

When BMP Is Still Used

Windows system graphics: Windows has historically used BMP for wallpapers, cursors, and icons — though modern Windows now uses PNG and WebP for these
Fax and printer drivers: some older printer drivers and scanning software output BMP because it does not require a decoder for the bitmap data
Graphics software intermediate format: some image editing workflows use BMP as a lossless intermediate — saving BMP between edits guarantees no quality loss between steps, unlike repeated JPEG saves
Embedded systems: some displays and microcontrollers use BMP because the format can be parsed with simple code — no compression algorithm needed

What BMP Cannot Do

No transparency (most cases): standard 24-bit BMP has no alpha channel. 32-bit BMP supports an alpha channel but it is inconsistently handled across applications
No metadata support: BMP has no built-in support for EXIF, IPTC, or color profiles — important for professional photo workflows
No animation: BMP is a single-frame format
Poor browser support history: while modern browsers can display BMP, it is not optimized for web delivery and has no place in web development

BMP vs. Other Formats

BMP vs. PNG: both are lossless, but PNG uses efficient compression that reduces file size by 60–80% with no quality loss. PNG also supports full transparency. There is almost no reason to use BMP instead of PNG
BMP vs. JPEG: JPEG uses lossy compression to achieve 10–20× smaller files. For photos where exact pixel accuracy is not needed, JPEG is better in every way
BMP vs. TIFF: TIFF is the professional lossless format — it supports CMYK, layers, metadata, and multiple pages. TIFF is the correct format when you need an uncompressed image for print; BMP is not

When to Convert BMP Files

Convert BMP to a modern format in almost every case:

For web use: convert to WebP or JPEG. WebP gives the smallest file size; JPEG is universally supported
For graphics with transparency: convert BMP to PNG. Use image compression after converting to keep PNG files small
For email or sharing: convert to JPEG at 80–85% quality. A 6 MB BMP becomes a 300 KB JPEG — 20× smaller with no visible quality loss for photos
For archiving: convert to PNG (lossless) or keep as BMP only if the receiving system requires it

BMP Format Quick Reference

Full name: Bitmap Image File
Extension: .bmp, .dib
Compression: none (or optional RLE, rarely used)
Transparency: no (32-bit variant yes, but inconsistent)
Animation: no
Color depth: up to 32-bit
Use today: legacy Windows systems, some printers, embedded displays
Better alternatives: PNG (lossless), JPEG (photos), WebP (web)