BMP and PNG are both lossless image formats — they store pixel data without any compression artifacts. The difference is how they store it. BMP stores raw, uncompressed pixel data: one byte per channel per pixel with no processing at all. PNG uses a lossless compression algorithm that typically reduces file size by 50 to 70% compared to BMP, with zero impact on image quality.
Converting from BMP to PNG is genuinely lossless — the output PNG contains exactly the same pixel data as the BMP. Nothing is changed, approximated, or discarded. You get a smaller file that looks identical.
How to convert BMP to PNG for free
The fastest method on any device — no software needed:
- Open the BMP file in your device's built-in image viewer (Photos on Windows, Preview on Mac).
- Go to File > Save As (Windows) or File > Export (Mac).
- Choose PNG as the output format.
- Save.
Both Windows and Mac handle BMP to PNG natively with no extra software. For a single file this is the quickest option. For multiple files at once, see the batch conversion section below.
Why PNG is better than BMP for almost everything
Smaller file size. A 1920 x 1080 BMP is about 6 MB of raw data. The same image as PNG is typically 1 to 3 MB — the same pixels, stored more efficiently.
Universal compatibility. PNG is supported natively by every browser, every operating system, every image editor, and virtually every platform that accepts image uploads. BMP is primarily a Windows format — it is not natively supported in most web contexts and can cause problems when shared across platforms.
Transparency support. BMP does not support transparent backgrounds. PNG does. If you need to convert a BMP of a logo or icon that should have transparency, you will need to manually remove the background in an image editor after converting — the conversion itself will not create transparency from a white background.
Web compatibility. Browsers do not display BMP files directly in the same way they display PNG. If you are using an image on a website, PNG is the correct lossless format.
Batch converting multiple BMP files to PNG
On Windows with IrfanView (free):Open IrfanView, go to File > Batch Conversion/Rename, add all your BMP files, set the output format to PNG, and run. IrfanView handles hundreds of files at once efficiently.
On Mac with Preview:Select multiple BMP files in Finder, right-click and choose "Open With > Preview". All files open in Preview's sidebar. Go to File > Export Selected Images, choose PNG as the format, and export. Preview converts all selected files at once.
BMP to PNG versus BMP to JPG — which should you choose?
It depends on the image content:
Choose PNG if the image is a screenshot, diagram, graphic with text, logo, or anything with flat areas of colour and sharp edges. PNG is lossless and keeps these images pixel-perfect.
Choose JPG if the image is a photograph with complex colour gradations. JPG will be significantly smaller than PNG for photographic content, and the quality difference at a good compression level is imperceptible. Use Filero's BMP to JPG tool for this.
Frequently asked questions
Is converting BMP to PNG completely lossless?
Yes. Both formats are lossless. The pixel data in the PNG output is identical to the pixel data in the BMP source. No quality is lost in the conversion.
Will the file size always be smaller as PNG?
For almost all real-world images, yes. In very rare cases — extremely noisy images with random pixel values at every position — PNG compression can produce a file as large as BMP because there are no patterns to compress. For photographs, screenshots, and graphics, PNG is always smaller than BMP.
Can I convert PNG back to BMP?
Yes, using the same tools — Paint on Windows or Preview on Mac can save a PNG as BMP. There is rarely a reason to do this unless a specific legacy system requires BMP input.
Ready to try it?
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