PixHow to Convert BMP to PNG (3 Free Methods)
BMP files store every pixel without compression, which means they are enormous and lack modern features like transparency. If you need to convert BMP to PNG, you get lossless compression (smaller files with zero quality loss) and full alpha transparency support. Here are three free ways to do it.
Why Convert BMP to PNG?
BMP was built for early Windows applications. It did its job when storage was cheap and the web did not exist. PNG does everything BMP does, but better.
| Feature | BMP | PNG |
|---|---|---|
| Compression | None | Lossless (DEFLATE) |
| Typical file size (1920x1080) | ~6 MB | ~1.5-3 MB |
| Transparency (alpha channel) | No | Yes |
| Web browser support | Partial | Universal |
| Color depth | Up to 32-bit | Up to 48-bit + 16-bit alpha |
| Metadata support | Minimal | Text chunks, ICC profiles |
| Animation support | No | No (use APNG or GIF) |
| Best use case | Legacy Windows apps | Web graphics, logos, screenshots |
The short version: PNG gives you smaller files, transparency, broader compatibility, and richer metadata. There is no practical reason to keep images in BMP unless a legacy application requires it.
For a deeper look at each format, see What is BMP? and What is PNG?.
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Method 1: Pixotter Online Converter
The fastest option. Pixotter's BMP to PNG converter runs entirely in your browser using WebAssembly. Your image never leaves your device -- no upload, no server, no waiting.
- Open pixotter.com/convert-bmp-to-png/ (or go to the general converter and select PNG as output)
- Drop your BMP file onto the drop zone
- Click Convert
- Download your PNG
That is it. Works on Chrome, Firefox, Safari, and Edge. No account required, no file size limits beyond your browser's memory, and your files stay private because nothing is transmitted.
If you are converting multiple BMP files, drop them all at once. Pixotter handles batch conversion in the same session.
Method 2: ImageMagick CLI
If you prefer the command line, ImageMagick (Apache 2.0 license) is the standard tool for image conversion on Linux, macOS, and Windows.
Install ImageMagick 7.1.x:
On Ubuntu/Debian:
sudo apt install imagemagick
On macOS with Homebrew:
brew install imagemagick
On Windows, download the installer from imagemagick.org/script/download.php.
Convert a single file:
magick input.bmp output.png
Batch convert every BMP in a folder:
magick mogrify -format png *.bmp
This creates a .png file alongside each .bmp in the current directory. The originals are untouched.
Convert and optimize PNG compression level:
magick input.bmp -quality 95 output.png
For PNG, the -quality flag controls the compression level (0-100, where higher means more compression effort, not more quality loss -- PNG is always lossless). A value of 95 tells ImageMagick to spend more CPU time finding the best compression, which produces smaller files.
Verify your conversion:
magick identify output.png
This prints the format, dimensions, color depth, and file size so you can confirm the conversion succeeded.
Method 3: Windows Paint / macOS Preview
No install needed. Both operating systems ship with tools that handle BMP to PNG conversion.
Windows Paint
- Open the BMP file in Paint (right-click the file, select Open with > Paint)
- Click File > Save as > PNG picture
- Choose your save location and click Save
Paint works fine for single files. For batch conversion, use Pixotter or ImageMagick.
macOS Preview
- Open the BMP file in Preview (double-click usually does it)
- Click File > Export
- Set Format to PNG
- Click Save
Preview also handles batch conversion: select multiple BMP files in Finder, right-click, Open With > Preview. Once all files are open, select them all in Preview's sidebar, then File > Export Selected Images and choose PNG.
BMP vs PNG: Detailed Comparison
Here is a more thorough breakdown to help you decide when each format makes sense.
| Criteria | BMP | PNG |
|---|---|---|
| File size (1080p photo) | ~6 MB | ~1.5-3 MB |
| File size (simple graphic/logo) | ~100-500 KB | ~5-50 KB |
| Compression type | Uncompressed (or RLE) | Lossless DEFLATE |
| Quality loss on save | None | None |
| Transparency | Not supported | Full alpha channel |
| Web usage | Not recommended | Standard |
| Email attachments | Often blocked or stripped | Accepted everywhere |
| Print workflows | Rarely used | Common |
| Editing round-trips | No degradation | No degradation |
| Software support | Windows-centric | Universal |
| Open standard | Microsoft-controlled | W3C recommendation |
Both formats are lossless, so converting BMP to PNG causes zero quality loss. You get a smaller file with more features. The only tradeoff is the CPU time spent compressing, which is negligible on modern hardware.
If your end goal is a photograph for the web, consider converting BMP to JPG instead. JPG uses lossy compression that shrinks photos dramatically. For graphics, logos, screenshots, or anything needing transparency, PNG is the right choice. See JPG vs PNG for a full comparison.
For even smaller web files, PNG vs WebP explains when WebP is the better option.
FAQ
Is converting BMP to PNG lossless?
Yes. PNG uses lossless compression, so every pixel in your original BMP is preserved exactly. The file gets smaller, but the image data is identical.
Why is my BMP file so large?
BMP stores raw pixel data without compression. A 1920x1080 image at 24-bit color uses roughly 6 MB (1920 x 1080 x 3 bytes). PNG compresses that same data to 1.5-3 MB with no quality loss.
Can I convert BMP to PNG without installing software?
Yes. Pixotter's converter runs in your browser and processes images client-side. No download, no install, no account. Windows Paint and macOS Preview also work without additional software.
Does PNG support transparency?
Yes. PNG supports a full 8-bit alpha channel, meaning each pixel can have 256 levels of transparency. BMP does not support transparency at all. This makes PNG the standard for logos, icons, and any graphic that needs to overlay other content.
Which is better for the web, BMP or PNG?
PNG. Every browser supports PNG natively. BMP support is inconsistent, file sizes are unnecessarily large, and no CDN or image optimization pipeline expects BMP input. Use PNG for web graphics, or consider WebP for even smaller sizes.
Can I batch convert BMP to PNG?
Yes, all three methods support batch conversion. Pixotter lets you drop multiple files at once. ImageMagick's magick mogrify -format png *.bmp converts an entire folder. On macOS, Preview can export multiple files simultaneously.
Will converting to PNG reduce image quality?
No. PNG compression is lossless. The pixel data in your PNG will be bit-for-bit identical to the BMP original. The file is smaller because PNG uses smarter data encoding, not because it throws away information.
What is the maximum image size PNG supports?
The PNG specification supports images up to 2,147,483,647 x 2,147,483,647 pixels. In practice, your system's RAM is the limiting factor. For very large images, the conversion may take a few seconds longer but the output is always lossless.
Wrapping Up
Converting BMP to PNG is straightforward with any of these three methods. Pixotter is the fastest if you want a browser-based solution with no install. ImageMagick 7.1.x handles batch jobs and scripting. Paint and Preview work when you just need a quick one-off conversion.
The result is always the same: a smaller file, full transparency support, and universal compatibility -- with zero quality loss.
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