BMP to PNG Converter

The conversion with no downside

Both BMP and PNG are lossless, so this changes the container without touching a single pixel value. What changes is the size. BMP writes every pixel out uncompressed; PNG runs the same data through DEFLATE with a per-row predictor first. Nothing is discarded and the file typically drops by 60–90%.

For flat content — screenshots, diagrams, scanned line art, anything from a piece of lab or office equipment — the reduction is at the high end of that range, because rows repeat and the predictor has a great deal to work with.

Prefer this over BMP to JPG when the image has text

The instinct with a huge file is to reach for JPEG, but JPEG's compression is designed for photographs and puts visible ringing around hard black-on-white edges. Scans of documents, screenshots, charts and engineering drawings all have exactly those edges. PNG has no such artefacts and still removes most of the bulk, so for anything text-like this is the better direction. JPG remains the right choice for photographic content where the last few percent of size matters.

Transparency survives

32-bit BMPs carry an alpha channel, and PNG stores one too, so transparency is preserved exactly. The far more common 24-bit and palette bitmaps have no transparency to begin with and convert without any special handling.

Where BMPs come from

Almost always a machine: scanners and multifunction printers, industrial and scientific cameras, older Windows software, and some medical and surveying equipment that has never been updated. The usual trigger for converting is that the next system in the chain — a web form, a document management system, an email attachment limit — refuses the file or chokes on the size.

Nothing is uploaded

Decoding and re-encoding happen in this tab using your browser's own image support. The file is never transmitted, which matters given how often a BMP turns out to be a scanned document or a medical image.

Common questions