BMP files have one defining trait: they are huge. A 1920 by 1080 image saved as a BMP weighs around 6 MB. The same picture as a JPG drops to roughly 300 KB, and as a WebP, closer to 150 KB. That single fact explains almost everything about BMP, where it came from, why it is rarely used today, and why the usual job with a BMP is converting it into something smaller. This guide explains what BMP files are and how to convert them, free and in your browser.
In this guide
What a BMP file is
BMP, short for bitmap, is an image format Microsoft introduced for early versions of Windows. It stores a picture in the most direct way possible: a grid of pixels, with the colour of every single pixel written out in full. The file extension is .bmp.
That direct approach makes BMP simple and reliable. Any program can read it without guesswork. It is one of the formats covered in our wider guide to image file formats, and it sits at the opposite end of the scale from a format like WebP. Where WebP works hard to make files small, BMP does no real compression at all.
Why BMP files are so large
A modern format looks at a photo and finds shortcuts. A stretch of blue sky is thousands of nearly identical pixels, so JPG or WebP store that region compactly instead of repeating the same value over and over. BMP does not look for shortcuts. It writes every pixel at full size, sky and all.
The result is a file 20 to 50 times larger than the same image in a compressed format. A desktop wallpaper that would be 400 KB as a JPG can reach 15 MB or more as a BMP. That weight is the reason you almost never want to keep an image as a BMP, send one by email, or put one on a web page.
Where you still run into BMP files
If BMP is so heavy, why does it still turn up? Because some software never moved on. Older Windows programs, certain scanners, some industrial and medical imaging devices, and a few specialised tools still produce BMP files by default.
So a BMP usually lands on your desk from somewhere else: a scan, an export from a legacy application, a file a colleague sends from an old system. You rarely choose to create one. The task is almost always the same, turn it into a smaller, more portable format.
Which format to convert a BMP to
The right target depends on what the image is and where it is going.
- PNG if the image is a graphic, a screenshot, or line art, or if it needs a transparent background. PNG is lossless, so sharp edges stay crisp.
- JPG if the image is a photograph headed for email or the web and you want a small file. JPG compresses photos efficiently.
- WebP if file size matters most. WebP produces the smallest result of the common formats and works in every current browser.
- GIF only if a specific platform or piece of software asks for a GIF. It is limited to 256 colours and is rarely the best choice otherwise.
How to convert a BMP file
Pick the converter that matches your target and drop the BMP onto it. Each tool runs in your browser, processes the file on your own device, and asks for no account.
- BMP to PNG, for graphics and anything that needs to stay lossless
- BMP to JPG and BMP to JPEG, for photographs that should be small
- BMP to WebP, for the smallest web-ready file
- BMP to GIF, when a platform specifically expects a GIF
Conversion is a one-way step. The new file is what you will use, but keep the original BMP until you have checked the result looks right, especially if you converted to a lossy format like JPG.
How to confirm a file is really a BMP
A file named scan.bmp is not always a BMP. Files get renamed and re-saved, and the extension can end up describing something the data is not. If a converter rejects your file, a format mismatch is a likely cause.
The BMP format checker reads the actual file data and confirms whether it is genuinely a BMP, so you know which converter you really need before you start.
Quick reference
| Your goal | Convert BMP to |
|---|---|
| Keep graphics and edges lossless | PNG |
| Small photo for web or email | JPG or JPEG |
| Smallest possible web file | WebP |
| A platform that requires GIF | GIF |
Frequently asked questions
Why is my BMP file so large?
BMP stores every pixel at full size with no real compression. That makes it 20 to 50 times larger than the same image as a JPG or WebP.
What should I convert a BMP to?
PNG for graphics and transparency, JPG for photographs, WebP for the smallest web file. GIF only if a platform specifically requires it.
Does converting a BMP lose quality?
Converting to PNG keeps every pixel exactly. Converting to JPG or lossy WebP discards a small amount of detail once, in exchange for a much smaller file. The BMP itself loses nothing in the process, so keep the original until you are happy with the result.
Can I open a BMP file without special software?
Yes. Almost every image viewer and browser can open a BMP. The problem is its size, not its compatibility, which is why converting it is usually worthwhile.
Is my file uploaded when I convert it?
No. These converters run inside your browser. The file is processed on your own device and is never sent to a server.