Images

What is BMP?

Short for Bitmap image file.

BMP is an early Windows image format that usually stores pixels uncompressed, producing large files that open almost anywhere.

By Utility Mule editorial team Last reviewed September 29, 2026 How we write guides

How it works

BMP dates from early versions of Windows. In its common form, it writes out every pixel’s color value in rows with little or no compression. That makes it simple to read and write, which is why old software and some scanners still produce it, but it also makes files very large.

Because the data is uncompressed, a BMP’s size is predictable: width × height × bytes per pixel, plus a small header. A 24-bit image uses three bytes per pixel whatever the picture shows, so a blank white canvas is as large as a detailed photo.

There is no quality to lose by converting BMP to PNG. PNG’s lossless compression stores the same pixels exactly while removing redundancy, and every website and application accepts it.

A practical example

A 1920 × 1080 screenshot saved as a 24-bit BMP is about 6 MB. The same screenshot as a PNG is often under 500 KB and looks identical.

What to watch out for

BMP files are rarely accepted by websites and are wasteful to email. Converting to PNG keeps every pixel exactly while making the file far smaller.

Tools you can use

Image Converter · Change an image from one format to another
Image Compressor · Cut file size with a visible quality trade-off

Go a little deeper

Common questions

Should I convert BMP to PNG or JPEG?

PNG keeps the image exactly as it is and suits screenshots, diagrams and graphics. JPEG makes a much smaller file for photographs but discards some detail.

Why are BMP files so large?

Most BMP files store every pixel’s color value directly with no compression, so size depends only on dimensions and color depth, not on what the picture shows.

Does BMP support transparency?

Some 32-bit BMP variants include an alpha channel, but many programs ignore it. Use PNG when you need transparency to survive.