Resize BMP

How to Resize BMP Images 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 New Size: In Resize, type a "Width" or "Height" in pixels or percent — with "Keep aspect ratio" on, the other side follows — or pick a "Size preset" (percent of original, a target height, or a platform size such as an Instagram post). The size 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 Resize BMP Images?

BMP is Microsoft's uncompressed raster format, originally introduced with Windows 2.0 in the late 1980s and still produced by Windows screenshots (Print Screen on older Windows builds), MS Paint, GDI+ tools, scanner drivers, and a long tail of industrial / scientific imaging software. A 1920×1080 24‑bit BMP weighs about 6.2 MB because BMP stores every pixel's raw RGB value with no entropy coding — the file size formula is essentially width × height × (bits_per_pixel / 8) plus a small header. Resizing is the most direct way to cut that down without leaving the BMP container.

• Trim Windows screenshots before sharing — A 4K screenshot saved as 24‑bit BMP is around 24 MB. Scaled to 50% (1920×1080) it drops to ~6 MB, easily small enough for Teams, email, or a bug-tracker attachment without converting away from the format your stakeholder expects.
• Feed legacy Windows or industrial software — CNC controllers, label-printer SDKs, microscopy platforms, and older Visual Basic apps often only ingest BMP. Resizing lets you bring high-resolution scans down to whatever the target system actually supports (often 1024×768 or 800×600).
• Prepare embedded display assets — Microcontrollers and small TFT panels typically expect raw BMP at the panel's native resolution (e.g., 320×240 for an ILI9341, 480×320 for an ILI9488). A right-sized BMP avoids runtime rescaling in firmware and saves precious flash bytes.
• Right-size for game / engine pipelines — Some build pipelines (older Unity importers, custom engines, Source-engine VTF tooling) accept BMP as the lossless intake format. Resizing source art to power-of-two dimensions like 512×512, 1024×1024, or 2048×2048 keeps mipmap generation predictable.
• Reduce scanner output for OCR / archival — Flatbed scanners often dump 600 DPI 24-bit BMPs that are 30+ MB per page. Halving the pixel dimensions (the pixel count of a 300 DPI scan) is plenty for OCR engines like Tesseract and shrinks each page by roughly 75%.
• Match a print or document spec exactly — Some agency forms or templates ask for a passport-style headshot or signature block in a fixed BMP size (e.g., 200×230 for India's UIDAI photo, 240×120 for some state DMV signature fields). A precise resize hits the spec without re-scanning.

BMP File Size by Resolution and Bit Depth

Sizes are pixel-data only (rows × ⌈bits_per_pixel × width / 32⌉ × 4 bytes per the BMP spec); the 14-byte file header and 40+ byte DIB header are negligible.

Resize Targets vs Original 1920×1080 24-bit BMP

Frequently Asked Questions

Does resizing a BMP lose any quality?

Downscaling resamples pixels with a bilinear/bicubic filter, so the output is a faithful smaller version of the original — no JPEG-style block artifacts, since BMP itself doesn't apply lossy compression. Upscaling, on the other hand, can't invent detail that wasn't there: pixels get interpolated and the result looks softer than a native high-resolution capture. For most workflows (screenshots, scans, app graphics), downscaling at 50–75% is visually indistinguishable from the original at the new display size.

Should I resize the BMP or convert it to PNG instead?

If your target software accepts PNG, BMP to PNG is almost always the better move: PNG is also lossless but uses DEFLATE compression, so a 6 MB BMP often becomes 500 KB–1.5 MB as PNG with no quality change. Keep BMP only when the consumer explicitly requires it — older Windows imaging APIs, certain CNC / label-printer SDKs, embedded display libraries, and some forensics tools that expect the uncompressed pixel layout. For a comparison of the lossless options, see BMP to TIFF and BMP to WebP.

Why is my resized BMP still huge compared to a JPG of the same dimensions?

BMP doesn't have entropy coding turned on by default — even after resizing, every pixel still costs 3 bytes at 24-bit color. A 1920×1080 photo is ~6 MB as BMP but might be 300–800 KB as JPG at quality 85, because JPG applies DCT-based lossy compression. If file size matters more than format compatibility, BMP to JPG gets you a 10–20× reduction. Inside BMP, the only lever this editor gives you is dimensions — it always writes 24-bit BMP; bit depth (drop from 24-bit to 8-bit indexed for ~66% savings) and file-size targeting are in our BMP compressor.

Can I keep an exact aspect ratio when entering width and height?

Yes. With "Keep aspect ratio" on (the lock button), enter one dimension and the other follows the source ratio — no distortion. Only with the lock off do a width and height that don't match the original ratio stretch the image. When a source's ratio is unfamiliar or awkward, a percent size (unit %) is safer than fixed pixel dimensions.

What's the largest BMP I can resize?

The editor can make an image up to 16384 px on a side and 120 megapixels, and it tells you when a size is past that ("Largest we can make is N px wide (120 MP limit)"). Opening is limited by how much memory your browser tab can hold, so a very large BMP (a 24-bit 16K × 16K file is around 768 MB) can be slow or fail to open, especially on a phone. If you're working with massive scientific or medical scans, scale them down in a desktop tool first.

Can I resize and reduce color depth at the same time?

Not in this editor — it has no colour-palette or bit-depth setting. Resize here, then save as PNG with "Save as" for a much smaller lossless file, or run the result through Compress BMP or a BMP converter for indexed or 1-bit output for legacy hardware.

Does the tool support BMP RLE compression?

The BMP file format spec defines RLE4 and RLE8 compression for 4-bit and 8-bit indexed images (per Microsoft's DIB header documentation), but it's rarely used because most BMP consumers expect uncompressed BI_RGB. This editor always writes uncompressed 24-bit BMP for maximum compatibility — there is no RLE option. If you want real compression, convert to PNG, WebP, or TIFF (LZW) using the linked converters above.

Can I batch resize many BMPs and apply the same setting to all?

Yes — drop up to 50 BMP files at once (a mixed batch works too). The size, format and quality you set apply to every file in the batch; "Download all (.zip)" saves every resized result in one ZIP, and "Download one by one" saves them separately.

What if I just need to crop, rotate, or compress instead of resize?

Use the dedicated tools: crop BMP for trimming to a region, rotate BMP for 90/180/270° turns or arbitrary angles, and compress BMP when dimensions are fine but the file is too big for email or storage.