Compress BMP online

BMP stores every pixel as it is — the format has almost no compression of its own. There is exactly one way to make the file smaller: use fewer colours.

Select the files you want to compress or convert and upload them here.

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Supported compression and conversion formats:
JPEG, JPG, PNG, GIF, WEBP, MP3, TIFF, TIF, BMP, DIB, RLE, JP2, JPF, JPG2, JPX, J2K, JPC, MJ2, OGG, OGV, SPX, WAV, 3GP, AAC, M4A, M4B, OPUS, OGA, MP4, AVI, MKV, MKA, SVG, EXR, RAW, ARW, SRF, SR2, CRW, CR2, CR3, DNG, DCR, KDC, ERF, 3FR, MEF, MRW, NEF, NRW, ORF, PEF, RAF, RWL, RW2, SRW, X3F, PDF, JXL.

You can upload files individually or as a ZIP archive.

Why BMP files are so heavy

BMP has no compression algorithm: a 1920 × 1080 image at 24 bits takes exactly 1920 × 1080 × 3 bytes — about 6 MB — no matter what is in it. A sunset photograph and a plain white rectangle weigh the same.

That leaves colour depth as the only working dial. Going from 24-bit (16.7 million colours) to 8-bit (256 colours with a fitted palette) makes the file three times smaller; going to 1-bit black and white makes it twenty-four times smaller. The palette is fitted to your image and transitions are smoothed with dithering, so you get fine stippling instead of banding.

Where this works and where it does not

Diagrams, logos, interface screenshots, scanned text — here 256 colours are indistinguishable from the original while the file drops to a third. Photographs take it worse: smooth sky and skin show visible steps, so rather than squeezing the palette, convert the shot to JPEG or PNG.

If a BMP came out of some old program and you need it for sending or publishing, converting usually beats compressing: the same picture as JPEG weighs dozens of times less and looks the same.

Common questions

How much smaller can a BMP get?

Exactly as much as the colour depth drops: 24-bit to 8-bit is three times, 24-bit to 1-bit is twenty-four times. The format has no values in between, so the size falls in steps rather than smoothly.

Can I compress a BMP without losing quality?

Only if the picture already uses fewer than 256 colours — then moving to a palette changes nothing visually. Otherwise some shades are lost: BMP simply cannot store them more compactly.

Should I compress a BMP or convert it to JPG?

For a photograph, convert: JPEG shrinks it dozens of times over with a near-identical result. Compressing BMP makes sense when the format cannot change — when some older program requires it.