BMP to JPG Converter

Why BMP files are so large

A standard 24-bit BMP stores three bytes for every pixel, whatever the picture contains, plus a 54-byte header. A 1200 × 800 BMP is therefore 1200 × 800 × 3 + 54 = 2,880,054 bytes, and a picture of nothing but white would weigh exactly the same. Our generated 1200 × 800, 1280 × 720 and 800 × 600 test BMPs matched this formula to the byte. It also means a 24-bit BMP reaches this tool's 20 MB upload limit at roughly 7 megapixels, which is about 3000 × 2300 pixels, before the pixel limit matters.

What changes when a BMP becomes a JPG

The BMP is decoded and re-encoded as a JPG at quality 85 out of 100. The quality is fixed, with no slider. Width and height do not change. Colour detail is stored at half resolution (4:2:0 subsampling), the usual JPG setting, so fine coloured detail such as thin red lines can soften slightly. JPG is lossy: the result is not an exact copy of the bitmap, and converting it back to a BMP will not restore what was discarded. A BMP does not carry EXIF data, and any colour profile in the file is not copied to the JPG.

Measured examples

Generated locally; not a benchmark; not a guaranteed result. The first three rows show the usual case: the BMP spends three bytes per pixel and the JPG spends a fraction of that. The last two show that a BMP with fewer bits per pixel starts out smaller, so there is less to win. A 1-bit image is tiny as a BMP, and JPG, which stores full-colour data, made it more than five times bigger. Check the size of the result before you delete a BMP.

Which BMP files are accepted

We converted 1-bit, 8-bit palette, 8-bit grayscale, 16-bit, 24-bit and 32-bit BMPs, an 8-bit BMP with run-length encoding, and a 24-bit BMP stored top-down instead of bottom-up. All of them converted, and the top-down file came out identical to the bottom-up one. We have not tested 4-bit, RLE4 or OS/2-style BMPs, so those may be rejected.

BMP transparency is not handled the way PNG transparency is. A 32-bit BMP carries an alpha byte per pixel, and this tool ignores it. In our test a BMP whose top rows were marked fully transparent came back with the colour values stored there, not a white fill, so a BMP that stores black under its transparent areas will show black. If you need a predictable white background, convert a PNG with PNG to JPG, which flattens transparency onto white.

When JPG is the right choice, and when it is not

JPG suits photographs, scans of photos and anything with smooth colour changes, and nearly every site, form and program accepts it. It is a poor fit for screenshots with small text, technical drawings and pixel art, where lossy compression can leave faint speckling around edges and a lossless format is the safer archive. This site does not offer a BMP to PNG converter, so for an exact copy use desktop software. The JPG vs PNG vs WebP guide explains how the formats compare, and the JPG compressor can shrink the result further at quality 75.

Accepts BMP (.bmp). Output is always JPG at the same dimensions. JPG, PNG and other formats are not accepted here. Limits: 20 MB per file, 12,000 px per side and 40 megapixels. One file is converted at a time.

1. Choose a BMP file (up to 20 MB). It is identified by its contents, not its extension.
2. Click "Convert BMP to JPG".
3. Download the result, named after your original with "-converted" added, and compare its size with the BMP before you delete anything.

• Shrinking a scan or screen capture that a legacy Windows program saved as BMP
• Uploading a bitmap to a website or form that only accepts JPG
• Reducing a folder of large uncompressed bitmaps before archiving or emailing them

Quality is fixed at 85 and cannot be changed. JPG is lossy and cannot reproduce a BMP exactly, and a BMP with only a few colours can become larger as a JPG. The alpha channel of a 32-bit BMP is ignored rather than flattened onto white. Some rarely used BMP variants, such as 4-bit, RLE4 and OS/2-style files, are untested and may be rejected.