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BMP

The BMP image format

BMP is Microsoft's bitmap format. It stores pixels in a simple, usually uncompressed way, which makes it easy for programs to read but produces very large files.

ConvertBMP → JPGBMP → PNGBMP → WebPBMP → PDFBMP → ICO

What it is

BMP, short for bitmap, is an image format that Microsoft has used in Windows since its early versions. It is also known as DIB, device-independent bitmap. The format is simple: a short header describing the image, optionally a color table, and then the pixel values row by row.

BMP supports several color depths, from 1 bit (black and white) up to 24 and 32 bits per pixel. A simple run-length compression exists for some low color depths, but most BMP files you meet are uncompressed.

Uncompressed means the file size follows directly from the pixel count. A 1920 x 1080 image at 24 bits per pixel needs 3 bytes per pixel, so 1920 x 1080 x 3 = 6,220,800 bytes, about 6 MB, no matter what the picture shows. A 12 megapixel photo of 4032 x 3024 pixels needs about 36.6 million bytes.

Strengths

  • Simple and lossless. Pixels are stored as they are, with no compression artifacts.
  • Easy to read. Old programs, embedded devices and simple software can handle BMP without complex decoders.
  • Native to Windows. Windows tools have supported BMP for decades.

Weaknesses

  • Huge files. Without compression, BMP files are many times larger than PNG or JPG versions of the same image.
  • Unsuitable for the web. Browsers can display BMP, but it is far too heavy for websites, and many upload forms reject it.
  • Limited transparency support. Alpha channels in BMP are not handled consistently across programs.
  • Little metadata. No standard way to store camera details like EXIF.

When to use it

Today, BMP is mostly something you receive rather than choose. Old software, industrial equipment, some scanners and certain programming tasks still produce or require it. If a system specifically asks for BMP, use it. Otherwise, store and share images as PNG (lossless) or JPG (photos).

How to convert BMP

The BMP converter works in both directions:

  • BMP to JPG, PNG or WebP: choose the output format; JPG is the default. PNG keeps every pixel exactly, while JPG and WebP make photos much smaller.
  • Images to BMP: choose BMP as the output when a program requires it. The output is 24-bit and uncompressed, without transparency; transparent areas are filled with a background color.

Other options:

Conversions run in your browser, so your files are not uploaded.

Frequently asked questions

Why is my BMP file so large?

Most BMP files are uncompressed, so every pixel takes up space regardless of the content. Converting to PNG keeps the image exactly and usually makes the file much smaller.

Will converting BMP to PNG lose quality?

No. PNG is lossless, so the pixels stay identical. Converting to JPG or WebP is lossy, but at a high quality setting the difference is hard to see.

Can BMP files be transparent?

Some BMP variants can store an alpha channel, but support differs between programs. For transparency, PNG is the reliable choice.