How to Convert BMP to PNG in Paint.NET

Paint.NET is the most popular free image editor for Windows and it handles BMP files natively. Converting a BMP to PNG takes about three clicks. There are a couple of quirks worth knowing — specifically around bit depth and the alpha channel — so this guide covers the full process and when you might hit a snag.

Opening a BMP File in Paint.NET

Paint.NET opens BMP files directly with no plugins required:

• Drag and drop: Drag the .bmp file from File Explorer onto the Paint.NET window
• File menu: File > Open (Ctrl+O), navigate to your BMP file, click Open
• Right-click in Explorer: Right-click the BMP file > Open with > Paint.NET

Paint.NET displays the image and shows the canvas dimensions and color depth in the title bar and status area. Most BMP files open as 24-bit RGB. Some older or specialized BMP files may open as 8-bit indexed color or grayscale.

Saving as PNG in Paint.NET

Once the BMP is open:

1. Go to File > Save As (Ctrl+Shift+S)
2. In the Save As dialog, change the Save as type dropdown to PNG (*.png)
3. Choose your filename and destination folder, then click Save
4. A PNG configuration dialog appears — the default settings (bit depth: Auto, interlacing: None) are fine for most images. Click OK.

That is the complete process. The resulting PNG is lossless — identical pixel quality to the BMP, typically 5-20x smaller file size.

Note: Do not use File > Save (Ctrl+S) — that overwrites the file in its original format. Always use Save As when changing formats.

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When Paint.NET Warns About 32-bit or Transparency

If Paint.NET shows a warning about saving as 32-bit PNG or asks about flattening the image, here is what it means:

A standard BMP has no transparency (alpha channel). When Paint.NET opens a BMP, the canvas has a white background layer. If you have added any layers or transparent areas during editing, the PNG save dialog may ask about bit depth:

• 32-bit (with transparency): Choose this if you want to preserve any transparent areas you added
• 24-bit (no transparency): Choose this if you just want a standard PNG matching the original BMP — slightly smaller file

If you want a completely flat PNG with no alpha channel and a white background (matching the original BMP exactly): go to Image > Flatten before saving. This merges all layers onto a white background and removes the alpha channel, producing a clean 24-bit PNG.

Batch Converting Multiple BMP Files in Paint.NET

Paint.NET does not include built-in batch processing. For batch BMP-to-PNG conversion, two options:

Option 1 — FileTypes Plus plugin: The FileTypes Plus plugin for Paint.NET adds more file format control but does not add batch processing on its own. For true batch conversion, you need the pyrochild plugin suite which includes a Script Lab tool for automation.

Option 2 — Use a different tool for batches: For converting a folder of BMP files, Paint.NET is not the fastest option. The browser-based BMP to PNG converter handles multiple files at once directly in the browser — no software setup. For command-line batch conversion on Windows, ImageMagick's mogrify command converts an entire folder in one command.

See the full batch BMP to PNG guide for step-by-step instructions on all methods.

When to Use a Browser Converter Instead of Paint.NET

Paint.NET is a great tool, but it is more steps than necessary for a simple format conversion:

• Open Paint.NET, wait for it to load
• Open the BMP file
• File > Save As > change format > OK

The browser converter is faster for one-off conversions: open the page, drop the file, done. It also works on any device — if you are on a laptop without Paint.NET installed, or on a phone or tablet, the browser approach requires nothing.

Use Paint.NET when you are already editing the image in Paint.NET and want to export as PNG at the end of your editing session. For pure conversion with no editing, the browser converter saves several steps.

Frequently Asked Questions

Does Paint.NET come pre-installed on Windows?

No. Paint.NET is a free third-party application available at getpaint.net. It is not the same as Microsoft Paint (which is pre-installed). Microsoft Paint can also open and save BMP files as PNG via File > Save as > PNG, though with fewer options than Paint.NET.

Is there a quality difference between BMP and PNG saved from Paint.NET?

No. PNG is lossless. Paint.NET preserves every pixel when saving as PNG. The PNG compression level setting only affects file size and save speed — it does not reduce image quality at any setting.

Can Paint.NET open all BMP variants?

Paint.NET opens most common BMP variants including 24-bit RGB, 32-bit RGBA, 8-bit indexed, and grayscale. Unusual variants like 1-bit monochrome or RLE-compressed BMP may not open correctly. If a BMP fails to open in Paint.NET, the browser converter uses a different image engine and may handle it.