BMP to JPG Converter

BMP is the Windows bitmap format: simple, but usually stored without compression, so a single screenshot or scan can take several megabytes. JPG compresses photos and scans to a fraction of that and is accepted by every website, email client and phone. This converter decodes each BMP with your browser — 1-, 4-, 8-, 16-, 24- and 32-bit files, run-length encoded (RLE) and old OS/2 bitmaps — and saves a JPG at the quality you choose. Nothing is uploaded.

How to use this tool

1. Drop one or more .bmp files into the box.
2. Set the JPG quality: 90% looks like the original, 75–80% gives much smaller files.
3. Choose a colour for transparent areas of 32-bit BMPs, and optionally a max width.
4. Download each JPG, or all of them as a ZIP; the table shows the size saved.

Formula

Uncompressed BMP size ≈ 54-byte header + height × (width × bits per pixel ÷ 8, rounded up to a multiple of 4 bytes). The JPG is the browser's JPEG encoding of the same pixels at quality q.

Every BMP row is padded to a multiple of 4 bytes, and nothing is compressed unless the file uses RLE, which is why BMPs are large. The header is read before decoding, so the table can show each file's bit depth, compression and header version. JPG has no transparency: the alpha channel of 32-bit BMPs is filled with the colour you pick.

Example

A 1920 × 1080 px, 24-bit screenshot.bmp is 54 + 1080 × 5,760 = 6,220,854 bytes (about 5.9 MB), because each row holds 1,920 × 3 = 5,760 bytes. Saved as JPG at 90% quality it is typically a few hundred kilobytes — more than 90% smaller — and looks the same on screen.