BMP Compressor

How to Compress BMP Files Online

1. Upload Your BMP Files: Drag and drop your .bmp images or click "+ Add Files" to browse. Batch upload of multiple bitmaps is supported in one session.
2. Pick a Quality Preset: Choose High, Medium, or Low under Image Compression. Because BMP itself has no general-purpose lossy mode, the preset is applied during processing — the larger gains come from resolution and dimension changes below.
3. Set Resolution or Target File Size (Optional): Keep original, scale by percentage (1-100%), select a preset from 4320p down to 144p, or type exact Width x Height in pixels. Switch to "Specific file size" to target an exact size in Bytes, Kilobytes, or Megabytes with Smart Scaling, which auto-adjusts dimensions to hit your number.
4. Compress and Download: Click "Compress." Files process in your browser session — no sign-up, no watermark, no email required.

Why Compress BMP Files?

BMP (Windows Bitmap) is the device-independent raster format Microsoft introduced with Windows in the mid-1980s. By default it stores every pixel uncompressed, so a 1920x1080 image at 24 bits per pixel works out to roughly 1920 x 1080 x 3 bytes plus header — about 6.2 MB on disk. The same image saved as PNG is typically 1-3 MB; as a quality-80 JPG, around 200-400 KB. That gap is why BMP is rarely a good choice for anything that needs to be emailed, embedded, or served on the web.

• Email and chat attachments — Gmail caps attachments at 25 MB and most BMP screenshots from a 4K display blow past that with two or three images. Compressing or converting brings them under the limit.
• Legacy Windows software — Older accounting, point-of-sale, kiosk, and CAD utilities still expect BMP input. Reducing resolution lets you keep the format while cutting the size that the host application has to load into memory.
• Embedded systems and microcontrollers — Devices that draw from indexed BMPs (digital signage, ATMs, ESP32 displays) benefit from 4-bit or 8-bit BMPs with RLE compression, which the Microsoft GDI spec supports natively.
• Medical and forensic imaging — Workflows that mandate lossless storage but use BMP for compatibility can still shrink files by reducing dimensions or converting to lossless PNG.
• Archiving scanned documents — A 300 DPI A4 scan can be 25 MB+ as a 24-bit BMP; reducing to 8-bit grayscale or converting to TIFF with LZW typically yields 70-90% smaller files.
• Game and texture asset cleanup — Old game mods often ship BMP textures. Down-scaling and re-encoding shrinks distribution size without forcing engine changes.

BMP File Size by Color Depth

These figures are derived from the BMP specification (header plus uncompressed pixel array; padding to 4-byte row boundaries adds a small overhead).

BMP vs Better-Compressed Alternatives

When to Compress vs Convert

Frequently Asked Questions

Can BMP itself be compressed without converting to another format?

Yes, but with limits. The Microsoft BMP specification defines two run-length encoding modes: BI_RLE8 for 8-bit (256-color) bitmaps and BI_RLE4 for 4-bit (16-color) bitmaps. These compress runs of identical palette indexes and work well for screenshots, line art, and indexed graphics. The spec does not define RLE for 1-bit, 16-bit, 24-bit, or 32-bit BMPs because those bit depths rarely contain long runs of identical bytes, so any encoding wins are negligible. For true-color photographs stored as BMP, the only practical size reduction is to lower the resolution or convert to a compressed format.

Why is my BMP so much larger than the same image as JPG or PNG?

Because BMP stores raw pixel data with no entropy coding. A 24-bit pixel takes 3 bytes whether it is part of a flat blue sky or a noisy texture. JPG applies discrete cosine transforms and quantization to throw away perceptually unimportant detail, often shrinking the file by 10-30x. PNG applies lossless DEFLATE compression with predictive filtering, typically shrinking it by 2-5x. BMP does neither by default.

What quality preset should I choose for compressing a BMP?

The Quality preset has the largest effect when the workflow re-encodes to a lossy intermediate, but for BMP itself the bigger lever is the resolution scaling on the next step. If you only need a thumbnail or preview, High at 720p or 1080p will produce a much smaller file than Low at the original 4K dimensions. Choose High when you need the cleanest result and rely on dimension reduction for the size win.

How does Specific file size mode work for BMP?

Enter a target (for example, 500 KB or 2 MB) and Smart Scaling estimates the dimensions and bit depth that will land near that number. Because BMP is essentially a fixed-size-per-pixel format, the math is predictable: target bytes divided by bytes-per-pixel gives you the pixel budget. The tool then picks dimensions that match your aspect ratio and stay within budget.

Will reducing color depth from 24-bit to 8-bit damage my image?

For photographs, yes — banding becomes visible because 256 colors cannot represent smooth gradients. For UI screenshots, icons, line art, and most flat-color graphics, 8-bit indexed (with a generated palette) looks identical to the 24-bit original at one-third the file size. If your BMP is going to be displayed at small sizes or printed at low resolution, the difference is usually invisible.

Are batch uploads supported?

Yes. Drop a folder of BMPs and the tool processes them in the same browser session. Settings such as Quality preset and target dimensions apply to all files, so a folder of 4K screenshots can be normalized to 1920x1080 with one click.

Is there a file size limit per upload?

XConvert processes files in the browser session without requiring sign-up. Very large multi-gigabyte BMPs (uncommon outside scientific imaging) may stress device memory; in that case, downscale before uploading or process in smaller batches.

Should I just convert BMP to PNG instead of compressing it?

For most modern workflows, yes. PNG is lossless, supports an alpha channel, and is decoded by every browser and image library shipped in the last 20 years. Per Google's WebP documentation, lossless WebP is on average 26% smaller than PNG again, so if your target supports it, BMP to WebP is the most space-efficient lossless path. Keep BMP only when a downstream tool refuses to open anything else.

Does compression run on your servers?

Files are uploaded for processing and removed after your session ends. There is no permanent storage, no account requirement, and no watermark added to the output.