Will the image degrade when I convert BMP to PNG?

No, there is no degradation at all. Both formats are lossless, meaning pixel values are stored exactly in the file. PNG spots repeating patterns and compresses them as it stores those values, but that compression does not change the data itself. When you open the PNG after conversion you will see exactly the same image that was in the BMP. The only thing that changes is how much space the file takes up on disk.

Can I delete the original BMP file after conversion?

Yes, for this conversion you can usually delete it safely. The PNG file contains all of the pixel information the BMP carried, so there is no informational advantage to keeping the BMP. The one exception arises if you need to feed the file as input to a program that accepts only BMP; in that case hold on to the original. Otherwise, deleting the BMP only frees disk space and costs you nothing.

Why did my PNG still come out large?

Because PNG works losslessly, its compression ratio depends entirely on the image's content. Images with flat colour areas, repeating patterns and a limited colour palette shrink dramatically. Noisy, densely textured or photographic content, by contrast, does not suit PNG's compression method and the file can stay larger than you expected. If that happens, your content is in fact photographic, and JPG may be a more appropriate target for sharing purposes.

Is transparency in the BMP carried over to the PNG?

If the source file genuinely has an alpha channel it can be carried over, but you need to be careful here. BMP's 32-bit variant can hold an alpha channel, but support for it is inconsistent across applications; many programs never write or read the alpha byte at all. So if you believe your BMP file has transparency, it is worth verifying by opening the converted PNG in a viewer that displays transparency. There is no problem on the PNG side; PNG supports the alpha channel completely and reliably.

How Do You Convert a BMP File to PNG?

The safest conversion

Most conversions between image formats involve a trade-off: you gain something and lose something. Going from BMP to PNG is one of the rare exceptions to that rule. There is nothing to lose here.

The reason is simple: both formats are lossless. BMP typically stores pixel data with no compression at all, while PNG stores the same data compressed with a lossless algorithm. The image you see on screen ends up identical — the only difference is that the PNG takes up far less space on disk.

So when a BMP lands in your hands and you cannot decide what to do with it, the right default answer is PNG.

What the conversion actually does

Understanding the gain correctly matters here. The conversion does not improve your image, sharpen it or fix its colours. If your BMP file is blurry, the PNG will be blurry too, because BMP already stores exactly the data that existed when it was saved.

The only thing the conversion does is package the same information far more efficiently. Where BMP writes out every pixel one by one, PNG spots patterns like "this colour repeats a hundred times in this region" and expresses them with a short description. For content rich in flat colour areas — screenshots, interface captures, logos and diagrams — this gain is very pronounced.

Step-by-step conversion

1. Take a quick look at the file's content

PNG is the right target for almost every BMP, but there is one exception: if the content is pure photography and your goal is to make the file as small as possible, PNG may not give you the reduction you want. The continuous colour variation in photographs does not lend itself to lossless compression. In that case converting the BMP to JPG gives a smaller file — but know that it is a lossy operation.

For every other kind of content — screenshots, scanned text, graphics, icons, drawings — PNG is both more accurate and usually smaller.

2. Upload the file

Drag and drop your .bmp file onto our BMP to PNG conversion tool. Files coming out of some older systems may carry a .dib extension; that refers to the same bitmap structure.

3. Verify the transparency situation

BMP's 32-bit variant can carry an alpha channel, but support for it is inconsistent across applications. The program that produced your file may have written the alpha information incorrectly, or not at all.

So if you believe your image should have transparent areas, open the converted PNG in a viewer that displays transparency against a chequered background and check. There is nothing to worry about on the PNG side — PNG supports the alpha channel completely and consistently. If there is uncertainty, that uncertainty comes from the source file.

4. Download the result and compare the size

When the conversion is finished, look at the sizes of the two files. For screenshot or graphic content the difference is usually striking. For photographic content the difference is more modest, but you still get a visible gain.

5. You can now delete the BMP

This is the reassuring part of this conversion. Because the PNG contains all the pixel information the BMP carried, there is no informational advantage to keeping the original. The one exception is if you need to give the file to a program that accepts only BMP; in that case keep the original.

If you are working with a lot of BMP files

An old archive folder, a stack of scanner output or asset files left over from an old project — you usually encounter BMPs in bulk rather than one at a time.

A few practical suggestions for that situation:

Test with one sample file first. Convert one file from the folder and check the result; you will see how transparency and colour behave before processing the whole folder.
Separate the content types in the folder. If the same folder contains both photographs and screenshots, splitting them in two gives better results than sending everything to the same target.
Preserve filenames. In an old project, asset files may be referenced by name; changing only the extension keeps the link intact in some workflows.

When is PNG not the right target?

Two cases, though rare:

Pure photographic content where the smallest possible file is required. JPG takes that further, at the price of being lossy.
When the target system accepts only BMP. If an old program, an industrial device or an embedded system is involved, do not convert; the format has to stay as it is.

In summary

Converting BMP to PNG is the cleanest way to make a file usable without losing anything. The pixels stay the same, the file shrinks, the format is supported everywhere, and transparency is carried over reliably. If you cannot decide what to do with the BMP in front of you, this conversion is almost always the right answer.