How to Convert BMP to PNG for Free: 5 Methods

BMP is one of the oldest and most wasteful image formats still in common use. A 1-megapixel BMP image takes up roughly 3 MB of disk space because it stores every pixel as raw, uncompressed data. Convert that same image to PNG and it shrinks to around 300 KB — a 10x reduction — without losing a single pixel of detail. This guide covers five free methods to convert BMP to PNG, from a one-click online tool to command-line batch processing.

Why Convert BMP to PNG?

BMP (Bitmap) was designed by Microsoft in the 1980s for Windows internal use. It has no compression by default, which makes it enormous compared to every modern format. Here is why PNG is a better choice in almost every situation:

• File size: PNG uses lossless compression that typically reduces a BMP by 70–90%. A 6 MB BMP screenshot becomes a 600 KB–1.5 MB PNG.
• Transparency: PNG supports a full alpha channel, allowing smooth transparent backgrounds. Standard BMP does not.
• Web compatibility: Every browser, CMS, and image editor reads PNG. BMP support on the web is unreliable and the file sizes are impractical.
• Lossless quality: Like BMP, PNG is lossless — no pixel information is discarded. Converting BMP to PNG preserves the image perfectly.
• Email and sharing: Most email clients and chat apps have file-size limits. PNG files pass through; BMP files often do not.

Method 1: Online Converter (Fastest, No Software Needed)

The quickest way to convert BMP to PNG is an online tool — no download, no install, works on any device.

1. Go to Picovert's Image Converter. The tool runs entirely in your browser, so your files are never uploaded to a server.
2. Drag and drop your BMP file (or multiple files for batch conversion).
3. Select PNG as the output format.
4. Click Convert and download the result.

This method works on Windows, Mac, Linux, and mobile. It handles batch conversion, so you can drop an entire folder of BMP files and get PNGs for all of them at once.

Method 2: Windows Paint (Built-in, No Download)

If you are on Windows, you already have a BMP-to-PNG converter installed. Microsoft Paint has supported PNG export since Windows XP.

1. Right-click the BMP file and choose Open with > Paint.
2. In Paint, go to File > Save as.
3. In the "Save as type" dropdown, select PNG picture.
4. Choose a location and click Save.

Paint converts one file at a time. For batch conversion — dozens or hundreds of BMP files — use Method 1 (online) or Method 5 (ImageMagick) instead.

Method 3: Mac Preview (Built-in on macOS)

macOS ships with Preview, which reads BMP files and exports to PNG with two clicks.

1. Double-click the BMP file to open it in Preview (default on macOS).
2. Go to File > Export.
3. In the Format dropdown, select PNG.
4. Optionally adjust the resolution. Leave it unchanged to keep the original pixel dimensions.
5. Click Save.

Preview also supports multi-file export: select multiple BMP files in Finder, open them all in Preview, then use File > Export Selected Images to batch-convert them to PNG.

Method 4: GIMP (Free, Full Control)

GIMP is a free, open-source image editor available on Windows, Mac, and Linux. It offers more control over the PNG output than Paint or Preview, including compression level and metadata options.

1. Download and install GIMP from gimp.org if you don't have it already.
2. Go to File > Open and select your BMP file.
3. Go to File > Export As.
4. Change the filename extension to .png or click "Select File Type" and choose PNG image.
5. Click Export, then adjust compression (0–9, lower = larger file but faster to decode) and click Export again to confirm.

GIMP's "Export As" (not "Save As") is the correct path for PNG. "Save As" in GIMP saves the native .xcf format.

Method 5: ImageMagick (Batch Convert via Command Line)

ImageMagick is a free command-line tool for Windows, Mac, and Linux. It is the best option when you need to convert large numbers of BMP files at once.

To convert a single file:

convert input.bmp output.png

To convert all BMP files in the current folder to PNG at once:

mogrify -format png *.bmp

The mogrify command overwrites files in place (keeping originals if the extension changes). To save to a different folder:

mogrify -format png -path ./output *.bmp

ImageMagick is available at imagemagick.org and can also be installed via Homebrew on macOS (brew install imagemagick) or via apt on Ubuntu (sudo apt install imagemagick).

BMP vs PNG: Quick Comparison

Shrink PNG Further After Converting

PNG lossless compression is efficient, but you can squeeze PNG files even smaller without losing quality. After converting from BMP, run your PNG through Picovert's Image Compressor. It applies additional optimization passes that typically reduce PNG size by another 20–40%, all while keeping the image pixel-perfect.