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Compress BMP Online

Shrink BMP files up to 99% — convert to JPEG, PNG, or WebP — 100% private, zero upload, instant download.

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Global Settings
Balanced
Low (high quality)High (small file)
Good balance — recommended for photos
Max Width (px)
Max Height (px)
Aspect ratio always preserved. 0 = keep original dimension.
Complete BMP Format Guide

Everything You Need to Know About BMP Files

The Bitmap Image File is one of computing's oldest image formats — raw, uncompressed pixel data that trades file size for absolute fidelity. Here's the complete picture: structure, compression options, and when to use each output format.

1986
Year introduced
54B
Header size
~99%
Max savings vs JPEG
32-bit
Max color depth

The Bitmap Image Format Explained

BMP (Bitmap Image File) stores pixel data as a direct, uncompressed grid of color values. What you see is literally what's on disk — every pixel's red, green, and blue channels written sequentially. No codec, no quantization, no data loss.

🧱

Raw Pixel Storage

BMP stores pixels row-by-row, bottom-up, with each row zero-padded to a 4-byte boundary. A 1920×1080 24-bit BMP takes exactly 6,220,854 bytes — no surprises.

📐

Bit-Depth Flexibility

BMP supports 1-bit (monochrome), 4-bit, 8-bit (paletted), 16-bit, 24-bit (true color), and 32-bit (with alpha). Modern BMP files are almost always 24-bit RGB.

⚡

Zero Decode Overhead

Since BMP data is already raw pixels, decoding is a trivial memory copy. This makes BMP ideal for real-time rendering pipelines where decode latency matters more than storage.

🖥️

Windows Native Format

BMP is the native bitmap format for Windows GDI (Graphics Device Interface). Every Windows API call that renders to screen ultimately works with BMP-compatible memory layouts.

🗜️

Optional RLE Compression

The BMP spec supports RLE (Run-Length Encoding) for 4-bit and 8-bit images. However, almost no software generates RLE-BMP, and many decoders don't support it reliably.

🌐

Universal Compatibility

Every image viewer, drawing app, and OS photo viewer since 1990 supports BMP. If you need a format that opens everywhere with zero software requirements, BMP is it.

Why BMP files are so large: A 3-megapixel photo stored as 24-bit BMP is approximately 9 MB. The same image as JPEG (quality 85) is roughly 1.2 MB — 7× smaller — because JPEG applies DCT-based frequency compression that removes visually imperceptible detail. BMP removes nothing.

BMP Binary File Structure

A standard 24-bit BMP file is made of three sections: a 14-byte file header, a 40-byte info header (BITMAPINFOHEADER), and the raw pixel data. The total size is always exactly 54 + width × height × 3 bytes (rounded up for row padding).

0x00
2B
Signature
0x42 0x4D ("BM")
0x02
4B
File Size
Total bytes (little-endian)
0x06
4B
Reserved
0x00000000
0x0A
4B
Pixel Data Offset
54 (0x36)
0x0E
4B
Header Size
40 (BITMAPINFOHEADER)
0x12
4B
Image Width
pixels (signed int32)
0x16
4B
Image Height
positive = bottom-up rows
0x1A
2B
Color Planes
Always 1
0x1C
2B
Bits Per Pixel
24 for true color
0x1E
4B
Compression
0 = BI_RGB (none)
0x22
4B
Raw Pixel Size
stride × height bytes
0x36
…
Pixel Data (BGR order)
rows padded to 4 bytes

Why BGR and not RGB? BMP was designed for x86 Windows, which stores multi-byte integers in little-endian order. Reading a 24-bit pixel as a 32-bit integer (0x00RRGGBB) becomes 0xBBGGRR00 on disk in little-endian — which is exactly the BGR byte order BMP uses. Modern BMPs may also store BGRA (32-bit with alpha padding). Row stride = ⌈width × 3 / 4⌉ × 4.

BMP vs JPEG, PNG, WebP — Complete Comparison

Choosing the right output format from this tool depends on what you're doing with the image next. Here's how each format compares across every dimension that matters.

PropertyBMP (24-bit)JPEGPNGWebP
CompressionNone (raw)Lossy DCTLossless DeflateLossy / Lossless
Typical size (3MP photo)~9 MB~1–2 MB~3–5 MB~0.6–1.5 MB
Quality lossNoneYes (ringing at high compress)NoneMinimal at high quality
Alpha transparencyNo (24-bit)NoYesYes
AnimationNoNoAPNG onlyYes
Browser supportChrome only (natively)UniversalUniversalAll modern browsers
Best forWindows dev, raw interchangePhotos, web imagesScreenshots, logosWeb, mobile apps
Decode speedFastestFastFastFast
Color accuracyExactNear-exact (subtle rounding)ExactNear-exact

Recommendation: For most use cases, convert your BMP to JPEG (photos) or PNG (graphics with sharp edges or transparency). Choose WebP for web delivery — it's universally supported in all modern browsers and gives the best file-size-to-quality ratio. Keep BMP only when the target application explicitly requires it.

BMP Compression Strategies That Actually Work

Since BMP itself has no built-in compression, "compressing a BMP" means converting it to a better format. Here's how to get the maximum size reduction without sacrificing what matters.

1

Match the output format to the image content. Photographic BMP files (gradients, smooth color transitions) compress best as JPEG. Flat-color graphics (logos, icons, screenshots) compress best as PNG or WebP. JPEG introduces ringing artifacts on sharp edges — switch to PNG or WebP for those.

2

Use compress levels 15–35 for photos, 40–65 for web thumbnails. On JPEG output, levels below 35 are almost indistinguishable from the original BMP at normal viewing distances. Levels above 75 introduce visible blocking and ringing on most photos.

3

Resize before compressing. The single biggest file-size driver is pixel count, not quality setting. A 4000×3000 BMP at compress level 20 is still larger than a 1920×1080 BMP at compress level 80. Use the Width/Height fields to resize to your actual display size first.

4

PNG with this tool uses UPNG color quantization. Unlike raw canvas.toBlob PNG (which is always lossless), this tool quantizes the PNG palette — like TinyPNG — giving 40–70% smaller PNG files at high compress levels. The quality difference is usually invisible at ≤ level 60.

5

WebP is almost always better than JPEG for web delivery. WebP's VP8 codec typically produces 25–34% smaller files than JPEG at equivalent perceptual quality. All Chrome, Firefox, Safari, and Edge versions since 2022 support WebP natively.

6

Use the "No upscale" option when resizing. If you enter a max dimension larger than the source BMP, the tool will upscale the image — this adds pixels without adding detail, wasting storage. Enable "No upscale" to prevent this for batch jobs with mixed-size inputs.

When to Use BMP (and When Not To)

BMP's raw, uncompressed nature is a bug in most situations — but a feature in a handful of specific use cases where absolute fidelity and zero decode complexity matter more than storage efficiency.

✅

Windows API Development

Win32 GDI, MFC, and DirectDraw all work directly with BMP-compatible memory layouts. HBITMAP objects are essentially in-memory BMPs. Keep BMP when passing images between Windows subsystems.

✅

Embedded Systems / Firmware

Microcontrollers driving LCD displays often need raw pixel buffers. BMP's known, fixed structure makes it trivial to parse without a full image codec library.

✅

Image Processing Pipelines

When reading an image in code to apply per-pixel transformations, BMP's direct pixel layout eliminates decode overhead. Read the 54-byte header, then stream pixel data directly into your processing loop.

🔄

Lossless Format Interchange

Using BMP as an intermediate between two lossy formats (e.g., converting JPEG→BMP→JPEG) is the right call — it prevents double-lossy degradation. Convert once to BMP, process, then convert to final format.

⚠️

Web Images — Convert Away

BMP files served on the web waste massive bandwidth. A 3 MP BMP hero image is 9 MB; the same image as WebP is under 300 KB. Browsers can display BMP, but they'll throttle your Core Web Vitals.

⚠️

Email Attachments — Convert Away

Most email clients can't display BMP inline. Recipients see a generic attachment icon instead of the image. Convert to JPEG or PNG before sharing by email or messaging app.

About Compress BMP Online

Convert and compress BMP files in your browser — no upload, no server, complete privacy. Compress BMP Online converts uncompressed BMP bitmap files to JPEG, PNG, or WebP, achieving 90–99% file size reduction while giving you full control over output quality.

BMP is an uncompressed format from 1988 that stores every pixel as raw RGB data — a typical 1920×1080 photo BMP is 6 MB regardless of content. Converting to JPEG or WebP applies modern compression algorithms that achieve 95–99% smaller files. Converting to PNG gives a lossless alternative that is still 70–90% smaller than BMP. This tool handles the conversion entirely in your browser using the native Canvas API.

Drop any number of BMP files, choose your target format and compress level, and the tool converts the entire batch in seconds. The before/after split viewer shows quality at a glance. Download results individually or as a ZIP archive. No account, no file size limits, no data leaves your device.

Features

  • BMP → JPEG/PNG/WebP — full format conversion with quality control; JPEG for photos, PNG for lossless, WebP for best ratio
  • Massive size reduction — 92–99% file size reduction from uncompressed BMP to modern compressed formats
  • 100% browser-local — Canvas API conversion, no upload, works offline, BMP files never leave your device
  • Unlimited batch — process entire BMP libraries at once with real-time per-file progress
  • Precise compress level — 1–100 slider for JPEG/WebP output quality; PNG output is always lossless
  • Smart resize — Max Width/Height with aspect-ratio lock; pairs with format conversion for maximum savings
  • Strip Metadata — removes embedded color profiles and metadata for extra savings
  • Before/After split viewer — compare original BMP with converted JPEG/PNG/WebP quality side by side
  • Batch ZIP download — get all converted files in one archive

How to Use

  1. Drop BMP files. Drag BMP bitmap files onto the drop zone or click Browse. Any number accepted.
  2. Choose output format. JPEG for photographic BMP content (recommended — smallest file). PNG for lossless conversion. WebP for best compression on modern browsers.
  3. Set compress level. For JPEG/WebP: level 8–20 gives near-lossless quality. For PNG output, compress level has no effect (PNG is always lossless).
  4. Optional: resize. Set Max Width/Height to your target display size for maximum savings.
  5. Compress All. BMP files are loaded, drawn to Canvas, and re-encoded in the target format. Large BMP files may take 1–2 seconds each.
  6. Download. Individual downloads or ZIP archive for the full batch.

Examples

Example 1 — Legacy photo archive: 40 BMP photos from old scanner (avg 7 MB each) → JPEG output, compress level 18, max width 2000 → avg 340 KB each → 95% savings → download ZIP.

Example 2 — Windows screenshot BMP: BMP screenshots from legacy Windows application → PNG output (lossless) → 75% smaller, text perfectly sharp, universal compatibility.

Example 3 — Engineering diagrams: BMP diagrams from CAD software → WebP output, compress level 10 (near-lossless) → 98% smaller than source BMP → suitable for web sharing.

Benefits

  • Extreme savings — converting BMP to JPEG or WebP achieves 92–99% file size reduction that compression alone cannot match.
  • Zero upload privacy — BMP files (which may contain sensitive screenshots or documents) are processed locally; they never touch a server.
  • Batch conversion — convert an entire BMP archive to web-ready JPEG/PNG/WebP in one session, no command-line tools needed.

Frequently Asked Questions

Why are BMP files so enormous?
BMP (Bitmap) is an uncompressed raster format created by Microsoft in 1988. Every pixel's color data is stored as raw RGB or RGBA bytes with no compression whatsoever. A 1920×1080 RGB BMP file is exactly 1920 × 1080 × 3 bytes = 5.93 MB, regardless of image content. A photo of a white wall takes the same space as a detailed painting. Modern formats like JPEG and WebP apply compression algorithms that reduce this dramatically.
How much smaller will my BMP be after conversion?
The reduction is dramatic: BMP to JPEG typically achieves 92–98% reduction. BMP to WebP achieves 94–99% reduction. BMP to PNG achieves 70–90% reduction (PNG is lossless). A 6 MB BMP photo becomes a 120–360 KB JPEG, 80–180 KB WebP, or 600 KB–1.8 MB PNG. The exact savings depend on image content (photos compress more than synthetic graphics).
What is the best format to convert BMP to?
For photos: JPEG at compress level 15–25 (visually lossless, 95–98% smaller). For graphics with transparency: PNG or WebP. For web content: WebP gives the best size/quality ratio and is supported in all modern browsers. For maximum compatibility without worrying about browser support: JPEG for photos, PNG for graphics.
Is converting BMP to JPEG lossless?
No — JPEG is a lossy format. The quality of the JPEG depends on the compress level you set. At compress level 8–15, the quality is nearly indistinguishable from the original BMP. At level 20–30, most people cannot see the difference for photographic content. Use the before/after preview to confirm quality at your chosen level before downloading.
Does BMP to PNG conversion lose quality?
No — PNG is a lossless format. BMP to PNG conversion is a lossless pixel-perfect operation. Every pixel's color is preserved exactly. The only difference is the compression algorithm (PNG uses DEFLATE, BMP uses none), which is why PNG is typically 70–90% smaller than the equivalent BMP. PNG is the ideal choice when you need zero quality loss.
Can BMP files have transparency?
BMP supports 32-bit RGBA (with alpha channel) in modern versions, but most BMP files are 24-bit RGB without transparency. When converting a 32-bit BMP with alpha to PNG or WebP, transparency is preserved. When converting to JPEG, transparent areas get a white background (JPEG has no alpha channel).
Can I batch convert BMP files?
Yes — drop any number of BMP files. All files are processed with your global settings (output format, compress level, resize). Real-time per-file progress shows original size, converted size, and percentage saved. Download all results as a ZIP or save individually.
Why would someone still use BMP format?
BMP remains in use in specific contexts: Windows system graphics (icons, wallpapers), some industrial imaging hardware, legacy software that only writes BMP, and situations where editing software requires an uncompressed source for repeated editing without generation loss. This tool converts those legacy BMP files to web-ready formats.

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