Crop BMP

How to Crop a BMP File Online

1. Choose Your BMP Files: Drag and drop BMP images onto the page or click "Choose BMP files" — up to 50 at once. The first photo opens in the editor and the rest line up as thumbnails below it; with two or more photos open, "Add more" adds files to the same batch.
2. Set the Crop: In Crop, pick an "Aspect ratio" ("Free", "Original", 1:1, 4:3, 16:9 and more) or a platform size, then drag the box on the photo or type its width and height under "Crop area". "Shape" switches between "Rectangle" and "Circle (avatar)". The crop applies to every photo in the batch.
3. Pick the Output Format (Optional): "Save as" keeps "Same as original" or saves as JPG, PNG, WebP or another format. For JPG, WebP and AVIF output, the "Quality" slider (40–100) trades file size against detail. Resize, Crop, Rotate and Flip all work in the same session, and "Undo" steps back.
4. Download: Click the Download button, which names the output format (for example "Download PNG"), for one photo, or "Download all (.zip)" for a batch — "Download one by one" saves the files separately. BMP files are processed right in your browser, so they are not uploaded. No sign-up, no watermark.

Why Crop BMP Files?

BMP (Windows Bitmap) was introduced with Windows 2.0 in 1987 as Microsoft's device-independent bitmap on disk. It stores raw pixel data with no compression by default (the BI_RGB scheme), which is why a 1920×1080 24-bit BMP weighs roughly 6 MB and a 4K BMP runs about 24 MB. Because file size scales linearly with pixel count, cropping a BMP is the most direct way to shrink it — every pixel you remove is bytes you remove.

• Trim Windows screenshots — Print Screen on legacy Windows builds and many enterprise capture tools save BMPs of the full desktop. Crop to the dialog or window you actually need before pasting into a ticket or doc.
• Clean up flatbed scanner output — Older TWAIN drivers and industrial scanners frequently write BMP at 24- or 48-bit depth. Crop the document edges, color bars, and platen borders out of multi-megabyte scans.
• Isolate regions for legacy CAD/GIS tools — Some Windows-only engineering, medical imaging, and machine-vision suites still ingest BMP because the layout is trivial to parse. Cropping lets you pass only the relevant tile.
• Prepare assets for embedded and industrial UIs — Resource compilers for older Windows applications, point-of-sale terminals, and embedded HMI panels often expect BMP icons and splash screens at exact pixel dimensions.
• Shrink files for archive or email — Because BMPs are uncompressed, cropping to half the area roughly halves the file. If you also need to fit a 25 MB Gmail attachment cap, save as PNG instead or use the separate Compress BMP tool.
• Anonymize before sharing — Crop out faces, badge numbers, or screen contents from a documentation BMP without re-encoding the rest of the image.

BMP vs PNG vs JPG — When to Keep BMP

For modern use, BMP to PNG typically cuts size 50–80% with no quality loss. Keep BMP only when the consuming software requires it.

Crop-and-Resize File Size Cheat Sheet (24-bit BMP)

Sizes assume 24-bit BI_RGB (3 bytes per pixel) plus a small header. An 8-bit indexed BMP would be about 3× smaller again, but this editor always writes 24-bit BMP.

Frequently Asked Questions

Does cropping a BMP reduce quality?

No. Cropping is a pure pixel-window operation — the colours of the kept region are written to the output unchanged (every BMP is written as 24-bit, and a 32-bit BMP with transparency is flattened onto white). Because BMP doesn't go through a transform-based encoder (unlike JPG), there is no re-compression artifact added by the crop itself.

How much does cropping shrink a BMP?

File size is roughly proportional to retained pixel count. Cropping to 50% of the area cuts size by about 50%; cropping to a quarter cuts it to about a quarter, plus a fixed ~54-byte header. This is a sharper size lever than any compression option, because the source had no compression to remove.

Can I keep transparency when cropping a BMP?

Not as BMP. The BMP this editor writes is always 24-bit with no alpha, so transparency in a 32-bit BMP is flattened onto white. (The alpha channel was added in BITMAPV3INFOHEADER and formalized in BITMAPV4HEADER — older 24-bit BMPs simply have no alpha to preserve.) If you need transparency, pick PNG under "Save as", or use BMP to PNG.

What bit depth is the cropped BMP?

Always 24-bit — this editor has no bit-depth setting. 24-bit keeps full color fidelity. An 8-bit (256-color palette) or 1-bit (black & white) source BMP is saved as 24-bit too, so its file can grow. If a legacy tool needs an 8-bit or 1-bit BMP, convert the cropped file in a desktop tool.

Why is my cropped BMP still bigger than the original JPG of the same scene?

Because BMP is uncompressed by default. Even a tightly cropped BMP carries 3 bytes per pixel (24-bit) with no entropy coding, while a JPG of the same dimensions runs through DCT, quantization, and Huffman coding. If size matters more than format compatibility, crop and convert to BMP to JPG or BMP to PNG.

Can I crop a BMP and combine it with image compression?

Not in this editor — BMP has no "Quality" slider and there is no compression setting. Crop here, then save as PNG with "Save as" (lossless and far smaller than BMP), or run the BMP through Compress BMP. Combined with a smaller crop area, that takes a 24 MB 4K BMP down by an order of magnitude.

Will the BMP still open in legacy Windows software after cropping?

Yes — the output uses the standard BITMAPINFOHEADER layout that every Windows version since Windows 3.0 (1990) reads. If your target is a very old or embedded tool that requires a specific bit depth, note that this editor always writes 24-bit, so check that the tool accepts it.

Can I crop several BMP files at once with the same dimensions?

Yes — drop up to 50 BMP files at once (a mixed batch works too). The crop region (or aspect-ratio preset) you set applies to every file in the batch; "Download all (.zip)" saves every cropped result in one ZIP, or use "Download one by one" to save them separately.

Should I crop as BMP or convert to a modern format first?

If the downstream consumer is a legacy Windows app, point-of-sale system, embedded HMI, or a tool that explicitly demands .bmp, keep the output as BMP. For everything else — web, email, mobile, modern documents — crop and convert to PNG (lossless, far smaller) or JPG (smallest, lossy). Adobe and Microsoft both recommend PNG over BMP for general-purpose lossless storage today.