PNG to BMP Converter — Convert PNG to Bitmap Online

When to Use BMP Format

Start with the honest answer: almost never, unless something is forcing you. Windows opens PNGs perfectly well — Paint, Photos, and File Explorer have done so for decades — and a PNG is smaller than a bitmap of the same picture while holding exactly the same pixels. What refuses your PNG is a specific program, and BMP is how you satisfy it:

• Legacy Win32 applications: in-house line-of-business tools, older utilities, and anything that reads pixels through the plain Win32 imaging calls will take a 24-bit BMP without complaint. Many were compiled before PNG was something a Windows program could assume.
• Machine vision and instrument software: lab, medical, and industrial inspection packages standardise on BMP because a frame is a header followed by raw pixels — no decoder, no library, no surprises, and no chance of a malformed compressed stream stalling a production line.
• Embedded systems and microcontrollers: there is nothing to decompress, so a bitmap can be streamed straight to a display. A PNG would need a zlib decoder, an unfiltering pass, and a frame buffer first — real work on a small chip.
• Windows resource pipelines and older SDKs: splash screens, toolbar strips, and installer graphics in long-lived codebases are often still specified as BMP because that is what the tooling was written for.

If none of those describe you, BMP is the wrong destination. Keep the PNG, or convert somewhere useful: PNG to WebP is smaller again for the web and keeps transparency; PNG to JPG is smaller still for sharing a photograph. Our image format by use case guide names a better target for web, print, email, and archive.

PNG vs BMP: File Size and Quality Differences

On quality the two formats tie, and that is worth saying plainly because people expect a catch. PNG and BMP are both lossless. Neither throws pixels away, so converting an opaque PNG to a bitmap changes nothing you can see — we converted an 800×600 photograph through the tool above and compared the result against the source pixel by pixel: not one of the 480,000 differed. There is no quality slider on this page because there is no compression to tune.

On file sizeit is a rout, and BMP loses every time. A bitmap stores every pixel uncompressed, so its size depends on the image's dimensions and nothing else — not the subject, not the detail, not how few colours you used. Three bytes per pixel, plus a 54-byte header and a little row padding:

Those figures are arithmetic, not estimates. The PNG side is the part that varies, and it varies enormously — which is why the same conversion can double your file size or multiply it by two hundred. We measured four real PNGs through this page's own converter:

Read that table as a single rule: the better PNG did its job, the worse BMP looks. A photograph barely doubles, because photographic noise is the one thing PNG's compression cannot do much with — that PNG was already close to raw. A screenshot grows elevenfold, because long runs of identical pixels are exactly what PNG is brilliant at and a bitmap writes every one of them out at three bytes each. The flat-colour icon is the extreme case: 273 bytes of PNG describe it perfectly, and the bitmap needs 192 KB to say the same thing. Unlike a lossy conversion, none of those bytes buy you anything — the picture is identical.

One quality caveat that is not about compression: if your PNG is 16 bits per channel, the bitmap will be 8. The converter decodes through a browser canvas, which holds 8-bit samples, so the extra headroom is gone before the BMP writer sees it. That matters for scientific and HDR source data, not for ordinary graphics.

What Happens to Transparency

This is the one way a PNG to BMP conversion can genuinely surprise you, so it is worth a minute. PNG carries a full alpha channel: a pixel is not simply see-through or solid, it can be any degree of partly transparent. That is how anti-aliased edges are drawn — the pixels around a curve are semi-transparent so the shape looks smooth against whatever is behind it.

The bitmap written here is 24-bit: three channels, nowhere to put alpha. Every pixel is composited onto white in proportion to its alpha before it is written. A fully transparent pixel becomes solid white; a half-transparent black pixel becomes mid-grey. So a logo cut out for a dark background does not merely arrive in a white box — its anti-aliased edges are blended toward white too. We converted a 512×512 logo with a soft edge and checked the result: its 4,478 partially transparent pixels came out pale, averaging 182 out of 255 in brightness. Placed on a dark background later, that edge reads as a light fringe around the shape. It is a limitation of 24-bit BMP rather than a quirk of this tool, and it cannot be undone afterwards — the alpha information is gone.

If the transparency matters, do not convert to BMP. The PNG you already have keeps it; WebP and TIFF keep it as well, and ICO is the right target if what you are really building is a Windows icon — that is the one Windows resource that genuinely needs an alpha channel.

How to Convert PNG to BMP on Windows and Mac

The converter above works on any operating system, handles several files at once, and never uploads anything — your browser decodes the PNG and the bitmap is assembled byte by byte in JavaScript on your own machine:

1. Drag your PNG file into the drop zone, or click to browse and select it.
2. Choose BMP from the Output Format menu.
3. Download the converted bitmap — it's saved straight to your device. Drop several PNGs at once and you can take them away together as a ZIP.

If you would rather use software already on the machine:

• Windows: open the PNG in Paint and choose File → Save as → BMP picture. Paint writes a 24-bit bitmap and flattens transparency, same as this tool. It does one file at a time.
• Mac: open the PNG in Preview, choose File → Export, then hold the Option key while opening the Format menu — BMP is hidden until you do. Preview will not show it otherwise, which is why people conclude a Mac cannot write BMP at all.

Both built-in options are fine for a single file. Neither does a folder in one go, which is the main reason to use the tool above.

Compatibility Notes for Windows Workflows

The file this tool produces is deliberately the most conservative variant of the format: a 24-bit, uncompressed BI_RGB bitmap with a 40-byte BITMAPINFOHEADER and bottom-up row order. That is the layout Windows has read since version 3.0 in 1990. There is no colour table, no run-length encoding, and no BITMAPV5 colour-space block for an older reader to choke on. If a program accepts BMP at all, it accepts this one.

• No alpha channel. 24-bit BI_RGB has nowhere to put transparency. Windows resource pipelines that need it — icons and cursors, chiefly — want a 32-bit BGRA image instead, so target ICO rather than BMP if you are building an icon.
• The header says 72 DPI. The bitmap records 72 DPI (2,835 pixels per metre) regardless of what the PNG's own pHYs chunk claimed. DPI is only a note about intended physical size and changes no pixels — set the real output resolution in whatever application does the printing.
• It is sRGB, with no embedded profile. BMP has no colour management to speak of, which is exactly why colour-critical print work uses TIFF instead.
• Watch the size on a network share. A folder of bitmaps is a folder of full-size, uncompressed files. Ten 12-megapixel images come to roughly 350 MB.

Going the other way is just as easy when the legacy step is done with: BMP to PNG gives you back exactly the pixels you started with, at a fraction of the size, because both formats are lossless.

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