Most people rarely think about BMP files until one suddenly appears: a scan from an office machine, an export from a piece of lab equipment, a screenshot from an old program, or an image from a kiosk or embedded device. The file is surprisingly large, and some modern apps handle it awkwardly. This guide explains why BMP is still around, when it is genuinely useful, and how to convert it sensibly.
What BMP is
BMP, short for bitmap, is one of the oldest image formats still in use. It became standard on Windows in the late 1980s. A BMP file stores the colour of each pixel in a simple grid, usually without compression. That makes it easy for software to read and write: a program can display a BMP with very little code.
Why BMP files are so large
Without compression, file size depends only on the number of pixels and the colour depth. A standard 24-bit BMP uses three bytes per pixel. A 1,920 by 1,080 image is about 6 MB, regardless of whether it shows a detailed photo or a plain white page. A 4,000 by 3,000 photo is about 36 MB.
Compare that with a typical JPG of the same photo at a couple of megabytes, or a PNG of a plain screenshot at a few hundred kilobytes, and you can see why BMP feels wasteful today.
Why BMP is still around
Simplicity
Writing a BMP file requires almost no processing, which suits machines with modest computing power, such as measurement instruments, industrial controllers and older office equipment.
Legacy software
Many long-lived business, scientific and educational programs were written when BMP was common, and they still use it.
Embedded and hobby devices
Small screens on microcontroller projects, digital signage and simple kiosks often load BMP images because decoding them is trivial.
Predictability
Because BMP is uncompressed, every pixel value is exactly what the device recorded, which some technical workflows value.
When BMP is genuinely useful
- When a device or program requires it.
- When you are building simple hardware projects that load images directly.
- When a technical process expects uncompressed pixel data.
In nearly every other case, a modern format is a better choice.
Converting BMP sensibly
For documents, scans, screenshots and graphics: PNG
BMP to PNG is lossless: every pixel stays identical, and files often shrink dramatically, particularly for scans and screenshots with large plain areas. This is the safest default conversion for BMP.
For photographs: JPG
BMP to JPG makes photos small enough to email and upload. Because a BMP has no previous compression, the JPG is compressed only once, from a perfect source, which gives an excellent result at quality 85.
For simple graphics on older systems: GIF
BMP to GIF suits icons, logos and diagrams with few colours, producing tiny files that work almost anywhere. Avoid it for photos, which become grainy.
Making a BMP from a modern image
Sometimes you need to go the other way, for an old program or a small device. AVIF to BMP creates standard 24-bit BMP files from AVIF images, with transparent areas filled by a background colour you choose.
A worked example: an office scanner archive
An accounting office has years of scanned invoices saved as BMP by an older scanner, each around 25 MB. Storage and backups are struggling. Converting the archive to PNG keeps every detail of each scan, including faint stamps and signatures, while shrinking files dramatically because most of each page is white. Backups that took hours now finish quickly.
A worked example: a weather display project
A hobbyist builds a small weather display that reads icons from a memory card in BMP format. Her icons are designed in a modern app that exports AVIF. She resizes each icon to the exact pixel size of the display area, converts them to BMP with a background colour matching the screen, and copies them onto the card.
Choosing the right target at a glance
If you are unsure which conversion to choose for a particular BMP, ask what the image contains:
- Text, lines, forms or screenshots? Convert to PNG. It is lossless, keeps every letter sharp, and shrinks these images dramatically.
- A photograph you want to share? Convert to JPG at quality 85 for the smallest file that still looks great.
- A simple icon or logo for an old website? Convert to GIF.
- Something precious you might need again? Convert to PNG, which preserves it exactly, and keep the original until you have checked the result.
Storage savings add up
For organisations with large BMP archives, converting to PNG can free a great deal of storage, shorten backups and make files easier to share, all without changing a single pixel. Because the conversion is lossless, it is safe for records where exactness matters.
Tips
- Convert scans and screenshots to PNG first. It is lossless and safe.
- Resize before converting to BMP for small screens, since BMP size grows directly with pixel count.
- Keep originals if the BMP is the only copy of something important, at least until you have checked the converted files.
Questions people ask
Is BMP lossless? Standard BMP stores pixels directly, so yes, but without compression.
Will converting BMP to PNG lose quality? No. PNG is lossless, so every pixel is identical.
Why does my device need BMP specifically? Usually because BMP is simple to decode on limited hardware.
Can BMP have transparency? Standard 24-bit BMP cannot. Some unusual variants can, but they are not widely supported.
In short
BMP survives because it is simple, predictable and built into older software and simple devices. For everyday use, convert BMP scans and graphics to PNG losslessly, photos to JPG, and simple icons to GIF. When a device or legacy program needs BMP, convert modern images into it, resizing first to keep files manageable.