If you have old scans, screenshots from older versions of Windows, images exported from engineering or medical software, or files from simple devices, you probably have BMP files. BMP stores every pixel without compression, so files are enormous. Converting them to PNG is one of the most satisfying conversions there is: the image stays pixel-for-pixel identical, but the file often becomes a fraction of the size. This guide explains how the BMP to PNG converter works.
Why BMP files are so large
A BMP file is essentially a list of colour values, one for each pixel. A 1,920 by 1,080 screenshot has over two million pixels. At three bytes per pixel, that is about 6 MB, even if the screenshot is mostly a plain white window.
PNG uses lossless compression. It finds patterns and repetition in the image and stores them efficiently. A mostly white screenshot compresses brilliantly, sometimes to just a few hundred kilobytes, and decompresses back to exactly the same pixels.
Lossless means truly identical
This point is worth stressing. Converting BMP to PNG does not lose any information about the image. Every pixel in the PNG is exactly the same colour as in the BMP. You can convert, compare, and find zero differences. That makes this conversion completely safe for documents, records and archives.
How much smaller will it be?
It depends on the content:
- Screenshots, diagrams and scanned text often shrink dramatically, frequently to a tenth of the size or less.
- Illustrations with flat colours also compress very well.
- Photographs shrink less, often to around half, because photos have fewer repeated patterns.
The result page shows the new size, so you can see the saving immediately.
Step by step
- Open the BMP to PNG tool.
- Choose your BMP file or drag it onto the page. The real file format is checked before upload.
- Press Convert to PNG.
- Download your PNG.
There are no settings to worry about. PNG compression is lossless, so the converter simply produces the best result.
A worked example: tidying an old archive
A small office has a folder of scanned forms from years ago, saved as BMP files of around 25 MB each. Storage is filling up and backups take forever. Converting each scan to PNG keeps every detail of the forms, including faint handwriting, but each file shrinks dramatically because most of each page is white paper. The folder becomes far easier to store, back up and share.
A worked example: sharing a screenshot
An older program saved a screenshot as BMP, and your email program warns that the 8 MB attachment is too large. Convert it to PNG and the attachment becomes small enough to send instantly, with text just as sharp as before.
Why not JPG?
JPG would make photographs even smaller, but it is lossy. For screenshots, diagrams and scans with text, JPG introduces faint smudges around letters and lines. PNG keeps them perfectly crisp. If your BMP is a photograph and you want the smallest possible file, BMP to JPG is an alternative. For everything else, PNG is the better choice.
Transparency
Most BMP files have no transparency. Some unusual BMP variants include an extra channel for it. When they do, PNG preserves it. Either way, the PNG looks exactly like the BMP.
Common mistakes to avoid
- Expecting quality to improve. Lossless conversion keeps the image exactly as it is. Blurry scans stay blurry.
- Converting to JPG by habit. For text and line art, PNG looks better and is often small enough.
- Deleting originals before checking. Open a few converted files to confirm everything looks right. Because PNG is lossless, it will, but checking is a good habit.
Who still uses BMP?
You might be surprised. Older Windows applications, scientific instruments, medical imaging exports, industrial machines, embedded devices and some educational software still produce BMP because it is simple to write. Converting their output to PNG makes it far easier to store and share.
Limits
The tool page lists the maximum file size and image dimensions. Because BMP files are large, very high resolution scans may approach the limit. If a file is too big, you will get a clear message before conversion.
Privacy
Your files are processed privately and never shared. Download links are personal and expire quickly. Uploaded and converted files are deleted automatically after a short retention period, and guest files are removed shortly after download.
Frequently asked questions
Is any quality lost? No. PNG is lossless, so every pixel is identical.
How much space will I save? Often a lot for screenshots and scans; less for photos.
Will PNG open on all computers? Yes. PNG is supported by every modern operating system, browser and image program.
Can I convert back to BMP if I need to? The image data is identical, so any image editor can save a PNG as BMP again without loss.
A short history of BMP
BMP, short for bitmap, has been part of Windows since its earliest versions in the 1980s and 1990s. It was designed for simplicity and speed on computers with modest processors. Storing pixels directly meant programs could read and display images with very little work. Storage was expensive, but images were small, so the lack of compression was acceptable.
As cameras and screens grew, images got much larger, and BMP's simplicity became a burden. PNG, introduced in the mid-1990s, offered lossless compression without the patent concerns of the time. Today PNG has replaced BMP for almost every everyday use, while BMP lingers in older software and devices that never needed to change.
Troubleshooting
The PNG is only slightly smaller. That happens with photographs and images with lots of noise, which compress less. It is still lossless. If you need a much smaller file and the image is a photo, consider JPG.
The page says my file is not a BMP. Some programs save other formats with a .bmp extension. The converter reads the real contents and tells you what the file actually is.
Colours look different in another program. Lossless conversion keeps the pixel values identical. If colours look different, compare both files in the same viewer, as different programs can display colours slightly differently.
In short
BMP to PNG is the ideal conversion for old, oversized images. You keep every pixel exactly, files shrink dramatically, and PNG opens everywhere. Use it for scans, screenshots, diagrams and archives, and choose JPG only if you have photographs and need the smallest possible files.