Dramatically smaller files
A BMP stores raw, barely compressed pixels, so it is often five to ten times the size of the same image as a PNG. Converting keeps every pixel but drops the wasted bytes.
ImageRuns in your browser
BMP to PNG Converter
Shrink a bulky Windows bitmap into a lossless PNG that the web actually accepts.
- Upload
- Batch upload supported · 25 MB max
- Privacy
- Nothing is uploaded
- Cost
- Free · no sign-up · no watermark
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Processed entirely on your device
Your file is read, transformed and re-encoded inside this browser tab using JavaScript. There is no upload endpoint — nothing leaves your machine, nothing is stored, and the result is created as a local object URL that disappears when you close the page.
Overview
About the BMP to PNG Converter
Convert BMP to PNG free online — turn an uncompressed Windows bitmap into a lossless PNG that is often many times smaller. Batch up to 20 files, no upload.
Why a BMP is so heavy
A Windows bitmap stores its pixels almost exactly as they sit in memory, with little or no compression. That makes the format simple and perfectly faithful, and it also makes it enormous: a modest 2000 × 1500 photograph can occupy nine megabytes or more as a BMP. PNG was designed for precisely this job — keeping every pixel losslessly while squeezing out the redundancy — so the same image is usually several times smaller with no visible change.
What the conversion does
The browser decodes the BMP into raw pixels, draws them onto a canvas, and re-encodes that canvas with the PNG encoder. Because both ends of the trip are lossless, the PNG is pixel-identical to the decoded bitmap. You are not trading quality for size here; you are dropping the wasted bytes a legacy container carries, which is why BMP to PNG is one of the few conversions that shrinks a file without giving anything up.
Batch conversion, privately
Up to twenty files convert in one run, each up to 25 MB, processed one at a time so memory stays predictable, and a summary strip totals the batch before and after so the saving is obvious at a glance. Each result is named after its source with a .png extension. Nothing is uploaded: the decode, the re-encode and every download happen inside the tab, with no account and no watermark, because there is no server on the other end.
When PNG is the wrong answer
BMP to PNG is almost always a win, but "almost." PNG's lossless modelling excels on flat colour — a UI screenshot or logo can drop ninety percent — yet it struggles with photographic noise, where a high-quality JPG can end up smaller than the PNG and look the same because it is allowed to discard data. If your bitmap is a scan of a photograph and size matters, compare against BMP to JPG before committing to lossless. The rule of thumb: crisp edges and few colours favour PNG; continuous-tone photographs with grain favour JPG.
Palette depth and hidden conversion costs
BMP is not one format: 8-bit indexed, 24-bit and 32-bit variants all exist, and an old indexed bitmap carries a palette that must be expanded to truecolour before the PNG encoder ever sees it. The expansion is lossless, but it means a 256-colour BMP gains no new colours — do not expect banding in the source to improve. If you are chasing the smallest lossless file rather than simply leaving BMP behind, run the result through the compressor, which re-tries the encoder's filters and bit depth without throwing a single pixel away.
Step by step
How to use the BMP to PNG Converter
Drop one or more images onto the upload area — a .bmp or any other format, which is detected automatically.
Optionally set a maximum dimension; anything larger is scaled down in the same pass.
Press Convert to PNG — each bitmap is decoded and re-encoded locally, one file at a time.
Read the result row: it names the format that arrived and how much smaller the PNG is.
Download each PNG on its own, or take the whole batch from the results list.
Why use it
Benefits and common use cases
What this tool is good for, and what it deliberately does not try to do.
Lossless, like the original
Both BMP and PNG are lossless, so nothing is thrown away in the conversion — the PNG is pixel-identical to the decoded bitmap, just far more efficient.
Web and design-tool friendly
Browsers, CMSs and design apps handle PNG natively, while a raw BMP is a legacy Windows format many web workflows refuse outright.
Private by construction
The decode and re-encode run in the browser's own image pipeline, so nothing is uploaded and no copy is stored.
Questions
Frequently asked questions
Short, honest answers about quality, limits and privacy.
What exactly is a BMP file?
BMP is the Windows bitmap format. It stores pixel data with little or no compression, which makes it simple and exact but very large. It was the native image type of early Windows and still appears from scanners, older software and some Windows utilities.
Does converting BMP to PNG reduce quality?
No. Both formats are lossless. The PNG holds precisely the pixels the BMP decoded, so the image looks identical — the only change is a much smaller file.
How much smaller will the PNG be?
It depends on the content. Flat images with large areas of one colour compress extremely well and can shrink by 90% or more; noisy photographs compress less but are still typically several times smaller than the raw bitmap.
Do I have to upload a BMP file?
No. The format is read from the file's bytes rather than its name, so a PNG, JPG, GIF, WebP, AVIF, TIFF or an iPhone HEIC converts to PNG here too. The output is always PNG.
Are my files uploaded to a server?
Never. There is no upload endpoint. The decode, the re-encode and every download happen inside your tab, and each result uses a local object URL released shortly after the click.