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PNG to BMP Converter

Data & Digital

Convert PNG images to uncompressed 24-bit BMP bitmap free online. Choose a background color for transparent areas and download instantly in your browser.

Reviewed by the thecalcu.com team · Last updated July 28, 2026

Drag & drop a PNG file here

or click to browse — max 15.00 MB, stays on your device

What is a PNG to BMP?

A PNG to BMP Converter takes a PNG image and writes it out as an uncompressed 24-bit bitmap, the classic BMP format built into Windows since its earliest versions. Where PNG compresses pixel data losslessly to keep files small, BMP in its standard form stores every pixel at full size with no compression at all, which makes it simple to decode but often much larger. Some legacy software and specific technical workflows still require BMP specifically, which is where this conversion becomes necessary.

This tool performs the conversion entirely in your browser: it decodes the PNG, composites any transparency over a background color you choose, and hand-assembles a standard BMP file byte by byte in JavaScript, no upload, no server round-trip. It pairs naturally with the BMP to PNG Converter for the reverse direction, and with the PNG to JPG Converter if you want a smaller alternative that still requires a background color.

Why Use a PNG to BMP Converter?

Certain legacy Windows applications, older embedded systems, and specific print or hardware pipelines accept only the uncompressed BMP format, rejecting or mishandling compressed formats like PNG or JPG. Converting a modern PNG asset into BMP on demand produces a compatible file without needing specialized bitmap-editing software.

A concrete situation this solves: preparing a PNG graphic or icon for legacy software, a driver installer, or an older technical tool that specifically expects an uncompressed BMP file rather than any compressed image format.

Who Should Use This Converter?

  • Developers and IT staff working with legacy Windows applications or embedded systems that require uncompressed BMP input.
  • Technical writers preparing assets for older documentation or installer tools with strict BMP requirements.
  • Anyone troubleshooting compatibility issues where a modern PNG is rejected by software that only understands classic bitmap files.
  • Hobbyists working with retro computing or legacy hardware that expects the simpler, uncompressed BMP structure.
  • Users needing a smaller alternative should consider the PNG to JPG Converter instead, since BMP files are typically much larger than compressed formats.

What Insights Does the PNG to BMP Converter Give You?

Once converted, the tool shows your Original (PNG) and Converted (BMP) side by side, along with the file size of each, usually the clearest illustration of how much larger uncompressed BMP storage is compared to PNG's compression, sometimes by an order of magnitude.

The Background color you select is baked permanently into any transparent areas of the source PNG, since standard BMP has no alpha channel, reviewing the converted preview confirms the chosen color reads correctly before you download it.

How to use this PNG to BMP calculator

  1. Drag and drop a .png file onto the upload area, or click it to browse your device.
  2. Choose a Background color to fill any transparent areas, white by default, or pick a custom color.
  3. Click Convert to BMP.
  4. Compare the Original (PNG) and Converted (BMP) previews and file sizes side by side.
  5. Click Download BMP to save the file, or Copy BMP to copy it directly to your clipboard.
  6. Click Change to start over with a different file.

Formula & Methodology

The browser decodes the PNG into a raw RGBA bitmap, composites it over your chosen background color, then writes a standard BITMAPFILEHEADER and BITMAPINFOHEADER followed by the pixel array in BGR byte order, stored bottom-up with each row padded to a 4-byte boundary, the exact structure required by the 24-bit BI_RGB BMP specification. Row size in bytes is calculated as ⌊(24 × width + 31) ÷ 32⌋ × 4.

For example, a 800×600px PNG icon at 120KB converts to a BMP of exactly 1,440,054 bytes (800 × 600 × 3 bytes per pixel, plus the 54-byte header, with no row padding needed since 800 × 3 = 2400 is already a multiple of 4), roughly 12 times larger than the compressed PNG, entirely due to the absence of compression.

Frequently Asked Questions

It decodes a PNG image, fills any transparent areas with a background color you choose, and writes the pixel data out as an uncompressed 24-bit BMP file, the classic Windows bitmap format. Because standard BMP has no compression, the resulting file stores every pixel at full size.
The entire conversion runs in your browser, and the file never leaves your device. The BMP file itself is hand-assembled in JavaScript from the decoded pixel data, with no server round-trip involved.
Some legacy Windows software, older embedded systems, and specific technical workflows still require the uncompressed BMP format specifically, rather than a compressed format like PNG or JPG. Converting on demand produces a compatible file without needing dedicated bitmap-editing software.
Standard 24-bit BMP has no alpha channel, so any transparent or semi-transparent areas in the source PNG must be filled with a solid color before writing the file. White is the default, but you can choose a custom color to match your target use case.
Almost always yes, often substantially, BMP's lack of compression means file size scales directly with pixel count, while PNG's compression can shrink the same image considerably. A PNG that's a few hundred kilobytes can easily become several megabytes as an uncompressed BMP.
Drag and drop your PNG file onto the upload area, choose a background color for any transparent areas, then click Convert to BMP. The converted file appears next to your original within moments, ready to download or copy.
No, BMP can store full-fidelity pixel data with no compression loss, so the conversion itself doesn't discard any detail beyond flattening transparency into your chosen background color. The result is visually identical to the source PNG apart from that background fill.
You can upload a PNG up to 15MB, which comfortably covers most screenshots, graphics, and design exports. Since the resulting BMP is uncompressed and can be considerably larger, very high-resolution images may take a moment longer to process.
Yes, the Copy BMP button copies the converted image directly to your clipboard in supporting browsers, so you can paste it straight into another application. If your browser doesn't support clipboard image writes, use Download BMP instead.
It produces a standard uncompressed 24-bit BMP (BI_RGB), the most widely supported BMP variant, readable by virtually any software that understands the format. It doesn't use run-length encoding compression or indexed color palettes.
File size isn't always the deciding factor, some legacy tools, drivers, or specific technical pipelines only accept BMP and will reject or mishandle PNG. In those specific cases, BMP's compatibility outweighs its larger size.
Also known as
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