Why is BMP so much bigger than PNG?

BMP is uncompressed — every pixel stored as 24 or 32 bits with no encoding. PNG uses DEFLATE compression (the same algorithm in ZIP files) which is lossless but significantly smaller. For a 4MP photo: ~12MB BMP, ~3-5MB PNG, ~1MB JPG. PNG matches BMP quality but is much smaller; JPG is even smaller if you accept slight pixel-level changes.

Will the PNG be exactly identical to the BMP?

Yes, pixel-for-pixel. PNG compression is lossless — the DEFLATE step doesn't discard data, just packs it more efficiently. A round-trip BMP → PNG → BMP would produce a binary-identical original.

What about animated BMPs?

BMP doesn't support animation — it's strictly a single-frame format. If you have animated content stored as a series of BMPs, convert each frame to PNG separately and assemble them in a video tool.

Why might a BMP fail to load?

Most likely it's the OS/2 BMP variant (rare but real) or a corrupted file. The browser supports Windows BMP v3, v4, and v5 but not the older OS/2 dialects. Open the BMP in another tool (GIMP, Paint.NET) to confirm whether it's actually readable.

Is the file uploaded anywhere?

No. The browser decodes the BMP locally via Canvas 2D, then re-encodes as PNG. No outbound network requests during conversion. Confirm via DevTools → Network.

Audio, Video & Voice · Free tool

BMP to PNG Converter

Convert BMP files to lossless, smaller PNGs instantly in your browser. Free online tool with no downloads or registration required for clean image conversion.

Updated June 2026

Conversion runs entirely in your browser — files never upload anywhere.

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What it does

Convert BMP (Bitmap) images to PNG. The classic Windows BMP format is uncompressed — every pixel is stored as its full RGB value with no compression — which makes BMP files massive. A 1920×1080 BMP photo is around 6 MB; the same image as PNG is typically 1–2 MB (lossless, identical quality), and as JPEG might be 200–400 KB at high quality. So if you've got a folder of old BMPs from a Windows app, scanned documents, or a legacy CAD/medical-imaging system, converting them to PNG saves dramatic disk space and makes them shareable on platforms that don't accept BMP (which is most modern web platforms).

PNG matches BMP's lossless quality — pixel-for-pixel identical output, just compressed. The DEFLATE algorithm PNG uses works best on images with large flat-color regions (icons, screenshots, line drawings) and still beats BMP handily on photographs. PNG also supports a real alpha channel for transparency, where standard BMP doesn't (a BMP with transparency is non-standard and won't render correctly in many tools — converting to PNG fixes that mismatch).

The conversion runs locally via Canvas 2D — drop your BMPs, download PNGs. Multi-file batch is supported. Works on any BMP variant your browser can decode (Windows BMP v3, v4, v5, but not the obscure OS/2 BMP variant).

Embed this tool on your siteShow snippet

Paste this snippet into any page. Loads on-demand (lazy), no tracking scripts, and sized to most dashboards. Replace the height to fit your layout.

<iframe src="https://freetoolarena.com/embed/bmp-to-png" width="100%" height="720" frameborder="0" loading="lazy" title="BMP to PNG Converter" style="border:1px solid #e2e8f0;border-radius:12px;max-width:720px;"></iframe>

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How to use it

Drop one or more BMP files (drag-drop or click to browse).
Each BMP is decoded by the browser, drawn to a Canvas, and re-encoded as PNG using the canvas.toBlob('image/png') API.
Click the download link next to each result. For batches of 10+ files, use the 'Download all' option to get a zip.
If a BMP fails to load, it's likely the unusual OS/2 variant or a corrupted file — try opening it in another image editor first to verify.

When to use this tool

Reducing disk space on archives of legacy BMPs (10× smaller as PNG, no quality loss).
Sharing BMP files on platforms that don't accept the format (Slack, Discord, most web galleries).
Adding proper alpha-channel transparency to images that came out of a BMP-only pipeline.
Migrating a folder of old screenshots or diagrams off BMP into a modern format.

When not to use it

When you need even smaller files and don't care about pixel fidelity — use BMP-to-JPG instead (often 10× smaller again at 90% quality, indistinguishable to the eye for photographs).
Specialized formats from medical imaging or CAD that happen to be BMP — those may have metadata that PNG drops. Check with the original tool.
BMPs where the file format itself is required (some legacy scientific or industrial systems) — keep them as BMP for compatibility.

Common use cases

Onboarding a colleague who needs the same calculation/conversion
Verifying a number or output before passing it on
Quick conversion during a typical workday
Pre-decision sanity-check on inputs and outputs

Frequently asked questions

Why is BMP so much bigger than PNG?: BMP is uncompressed — every pixel stored as 24 or 32 bits with no encoding. PNG uses DEFLATE compression (the same algorithm in ZIP files) which is lossless but significantly smaller. For a 4MP photo: ~12MB BMP, ~3-5MB PNG, ~1MB JPG. PNG matches BMP quality but is much smaller; JPG is even smaller if you accept slight pixel-level changes.
Will the PNG be exactly identical to the BMP?: Yes, pixel-for-pixel. PNG compression is lossless — the DEFLATE step doesn't discard data, just packs it more efficiently. A round-trip BMP → PNG → BMP would produce a binary-identical original.
What about animated BMPs?: BMP doesn't support animation — it's strictly a single-frame format. If you have animated content stored as a series of BMPs, convert each frame to PNG separately and assemble them in a video tool.
Why might a BMP fail to load?: Most likely it's the OS/2 BMP variant (rare but real) or a corrupted file. The browser supports Windows BMP v3, v4, and v5 but not the older OS/2 dialects. Open the BMP in another tool (GIMP, Paint.NET) to confirm whether it's actually readable.
Is the file uploaded anywhere?: No. The browser decodes the BMP locally via Canvas 2D, then re-encodes as PNG. No outbound network requests during conversion. Confirm via DevTools → Network.

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