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BMP to PNG converter

Convert BMP images to PNG format

No watermarkFree & unlimited
All processing happens in your browser. No data is sent to any server.

This is the rare conversion with no downside. A bitmap stores three raw bytes per pixel and compresses nothing; PNG applies prediction filters and deflate to exactly the same pixel values and typically stores them in a fraction of the space. Nothing is approximated, nothing is rounded, and converting back later would return the identical image. Bitmaps usually turn up as output from older Windows software, scanners, screen-capture utilities and embedded devices, and every one of those files is carrying a great deal of avoidable weight.

Key facts about BMP to PNG converter

Key facts about BMP to PNG converter
Pixel fidelityExact. PNG compression is lossless, so every RGB value in the bitmap survives unchanged - this is a repackage, not a re-encode.
Typical reduction80 to 95 percent for screenshots and interface captures. A 6.2 MB 1920x1080 bitmap commonly lands between 200 KB and 900 KB.
Photographic sourcesShrink less - noisy camera content often lands at 40 to 60 percent of the bitmap, because deflate cannot predict random texture.
How PNG winsRow filters predict each pixel from its neighbours and deflate compresses the residuals, which is devastating against flat colour and gradients.
TransparencyThe output is opaque. Standard 24-bit bitmaps carry no alpha, and converting does not create any.
MetadataThere is none to lose - bitmap headers contain no EXIF, no colour profile and no timestamps, only geometry.
DecodingHandled by the browser's own bitmap support. Unusual variants such as RLE-compressed or OS/2-style files may fail to decode and report an error.
Quality optionsNone, and none are needed - PNG has no quality setting, so the only lever is an optional downscale.
Opens natively inEvery browser, phone, editor, office application and upload form - PNG is as universally accepted as an image format gets.

What happens to your file

The bitmap is turned into an object URL, decoded by the browser's built-in BMP support, drawn onto a canvas and re-encoded by canvas.toBlob with image/png, which invokes the PNG compressor already inside the browser. Large bitmaps are handled entirely in this tab's memory - a 100 MB file is never uploaded anywhere, which is also what makes it practical, since transferring bitmaps of that size to a service and back would dominate the time.

About this tool

  1. 1

    Add the bitmaps

    Up to twenty .bmp files per run. Large files are fine; the size cap is 500 MB each.

  2. 2

    Leave the settings alone

    There is no quality control on this page, because nothing about the conversion is lossy.

  3. 3

    Resize only if you want fewer pixels

    The presets change the image itself. Skip them when you are converting purely to save space.

  4. 4

    Convert and check the saving

    The result panel reports both sizes and the percentage saved - on interface captures it is often above ninety percent.

Specs & compatibility
Input and outputTakes .bmp only (image/bmp) and returns .png with the image/png type; any other extension is refused before decoding.
Conversion pathBMP to PNG runs in three steps: an <img> element decodes the bitmap, 24-bit and 32-bit variants alike; the pixels land on a 2D canvas in this tab; then canvas.toBlob with the image/png type returns the finished file.
Browser supportThe bitmap side decodes in every current browser, while writing the PNG is just as universal, canvas.toBlob having produced it since canvas existed.
Controls for this pairNo quality slider, PNG not being a lossy target here, so the max-dimension presets from 3840 down to 200 px are the only way to hold the PNG down in size against the BMP.
Batch, caps and namingTwenty BMP files per run at 500 MB each; one result downloads as a single PNG, several as converted-png-files.zip, zipped by JSZip 3.10 in page memory.
Device ceilingThe canvas caps it: past roughly 16,384 px a side Chromium refuses the bitmap and iPhone Safari gives up sooner, so an oversized BMP fails before any PNG bytes exist.
  • Converting a folder of legacy bitmaps to PNG is one of the cheapest disk-space wins available, since the images themselves are unchanged.
  • Screenshots and UI captures compress best because they contain long runs of identical pixels, which is exactly what PNG filters target.
  • If the bitmap fails to load, it is probably an RLE-compressed or OS/2 variant; re-saving it from Paint as a standard 24-bit bitmap fixes it.
  • Need it even smaller and the content is photographic? Convert to WebP or JPG instead - PNG stays lossless, which costs bytes.
  • Archiving output from older Windows applications, scanners or test equipment without losing a single pixel.
  • Preparing bitmap screenshots for a bug report, wiki or document where a multi-megabyte attachment is impractical.
  • Migrating a legacy image library to a format that current software and upload forms actually accept.
None whatsoever. PNG compression is mathematically lossless, so the decoder reconstructs precisely the values the bitmap contained. Converting the PNG back to a bitmap would produce the same pixels you started with. The only thing that changes is how efficiently those pixels are stored.
For screenshots, interface captures and flat graphics, usually 80 to 95 percent smaller. For photographs the saving is more modest, often landing at half the bitmap, because photographic noise resists prediction. A bitmap's size depends only on its dimensions, so the saving depends entirely on what the picture shows.
Browsers read the common 24-bit and 32-bit uncompressed forms, but a file using RLE compression, an OS/2 header or an exotic bit-field layout may be refused by the decoder, which surfaces as a conversion error. Opening it in Paint and saving it again as a standard 24-bit bitmap is usually enough.
No. A typical bitmap is 24-bit with no alpha channel at all, so there is nothing to carry over and the PNG is opaque throughout. Making a background transparent is an editing operation, not something a format conversion can infer.
PNG if the pixels must stay exact or the files will be edited further - it is lossless and accepted everywhere. WebP if the goal is the smallest possible file: lossless WebP typically beats PNG by a further fifth, and lossy WebP goes much smaller still if the content is photographic.

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