BMP or JPG: Which Is Better?
For almost everything, JPG. A Full HD BMP is about 5.9 MB (1920 × 1080 pixels × 3 bytes), while a good-quality JPG of the same image is roughly 300 KB. BMP only wins when software requires it, or when you need lossless pixels and cannot use PNG.
What Is BMP (Windows Bitmap)?
BMP, short for Bitmap Image File, is one of the oldest image formats in use today. Developed by Microsoft (together with IBM for OS/2) and used since the early days of Windows, BMP stores image data as a grid of pixels with virtually no compression. Each pixel's color value is written directly to the file, making BMP simple but extraordinarily large.
A BMP file consists of a file header, an information header (DIB header), an optional color palette, and raw pixel data. The format supports 1-bit monochrome, 4-bit (16 colors), 8-bit (256 colors), 16-bit, 24-bit, and 32-bit color depths. The most common variant is 24-bit BMP, which stores 3 bytes per pixel (red, green, blue).
Although BMP technically supports RLE (Run-Length Encoding) compression, this option is rarely used. In practice, virtually all BMP files are uncompressed.
Key point: A 1920×1080 photograph stored as a 24-bit BMP is approximately 5.9 MB. The same image as a JPG at high quality is roughly 200–400 KB — that is a 15–30x size reduction.
Why Are BMP Files So Large?
BMP files are large because they store every pixel independently, with no compression. Here is how the math works for a standard 24-bit BMP:
- Each pixel = 3 bytes (one byte each for red, green, blue)
- 1920 × 1080 image = 2,073,600 pixels × 3 bytes = 6,220,800 bytes ≈ 5.9 MB
- 4K image (3840 × 2160) = 8,294,400 pixels × 3 bytes ≈ 23.7 MB
By contrast, JPG uses lossy compression (DCT-based) that exploits the way human vision works. It discards information the eye barely notices, achieving compression ratios of 10:1 to 50:1 depending on quality settings.
| Image Resolution | BMP Size (24-bit) | JPG Size (quality 85) | Size Reduction |
|---|---|---|---|
| 640 × 480 | 900 KB | ~50 KB | ~18x smaller |
| 1280 × 720 (HD) | 2.6 MB | ~140 KB | ~19x smaller |
| 1920 × 1080 (Full HD) | 5.9 MB | ~300 KB | ~20x smaller |
| 3840 × 2160 (4K) | 23.7 MB | ~1.2 MB | ~20x smaller |
BMP vs JPG: Full Comparison
Here is a detailed comparison of the two formats across every important dimension:
| Feature | BMP | JPG |
|---|---|---|
| Compression | None (uncompressed) | Lossy (DCT-based) |
| File size | Very large | 10–50x smaller |
| Quality | Pixel-perfect (lossless) | Near-original (adjustable quality) |
| Transparency | 32-bit BMP supports alpha | No transparency support |
| Color depth | 1 to 32-bit | 24-bit (16.7 million colors) |
| Web support | Displays in browsers, but rarely used on websites | Universal browser support |
| Metadata (EXIF) | Not supported | Full EXIF, IPTC, XMP support |
| Email/sharing | Too large for practical sharing | Standard for photos |
| Social media | Not accepted by most platforms | Universally accepted |
| Printing | Accepted by some print shops | Standard print format |
Why BMP Still Exists Today
Given its massive file sizes and lack of web support, you might wonder why anyone still encounters BMP files. There are several reasons:
- Legacy Windows applications: Some older Windows programs (medical imaging, industrial equipment, SCADA systems) only export BMP because they were written in the Windows 3.1 or Windows 95 era
- Screenshots on older systems: Windows Paint historically saved screenshots as BMP by default
- Embedded systems: Some embedded hardware (printers, CNC machines, digital signage) use BMP because it requires zero decompression overhead
- Clipboard operations: When you copy-paste images in Windows, the clipboard stores data in BMP format internally
- Simplicity: BMP is trivially simple to read and write in code. Many programming tutorials use BMP as a first image format because the parsing logic is straightforward
In modern workflows, BMP is almost never the right format for the final output. If you receive BMP files from legacy systems, scanners, or old software, converting them to JPG (for photos) or PNG (for graphics with transparency) is the right move.
When to Convert BMP to JPG
Converting BMP to JPG is appropriate in almost every scenario involving photographic or complex images:
- Sharing by email: A 5.9 MB BMP becomes a 300 KB JPG — that is the difference between bouncing off inbox limits and sending instantly
- Uploading to the web: browsers can show BMP, but the files are far too heavy for web pages, and many site builders reject them. JPG is the standard web photo format
- Social media: many platforms reject BMP uploads, and the rest convert them anyway. JPG is the safe choice
- Archiving photos: A folder of 1,000 BMP screenshots at 6 MB each takes 6 GB. As JPGs, the same folder is under 300 MB
- Batch processing: When migrating data from legacy systems that generated BMP outputs
When NOT to convert to JPG:
- If the image has sharp text, line art, or flat colors — use PNG instead (lossless, handles edges better)
- If you need transparency — use PNG or WebP (JPG does not support alpha channels)
- If the image will be edited further — keep it lossless until final export. Why that matters is explained in lossy vs lossless compression.
Batch Conversion Tips
If you have a large collection of BMP files to convert, here are some practical tips:
- Quality setting: JPG quality 85–90 is the sweet spot for photographs. Below 80, compression artifacts become visible. Above 95, file size increases rapidly with minimal visual improvement
- Resolution check: BMP files from old systems may be at low resolution (640×480, 800×600). These will produce small JPGs regardless of quality settings
- Color mode: Some BMP files are 8-bit (256 colors) or even 4-bit (16 colors). These convert fine to JPG but may not look great if they were originally screenshots of colored UI elements
- Naming convention: When batch converting, preserve the original filename and only change the extension
Tip: CleverUtils converts one BMP per upload, at quality 92 by default (60, 80 and 100 are the other options). What each level costs in size and detail is explained in JPEG quality settings: Q80 vs Q90 vs Q100. For hundreds of files, IrfanView’s batch conversion or ImageMagick’s mogrify -format jpg *.bmp is faster.
How to Convert BMP to JPG in Paint, Preview and Online
Windows Paint
- Open the BMP in Paint.
- Choose File → Save as → JPEG picture.
- Name the file and click Save.
Mac Preview
- Open the BMP in Preview.
- Choose File → Export, set Format to JPEG and adjust Quality.
- Click Save.
Online
Upload the BMP to the CleverUtils BMP to JPG converter, keep quality 92 or pick 60, 80 or 100, and download the JPG. Transparent areas in 32-bit BMPs are filled with white.