How to Convert BMP to PNG: 5 Free Methods in 2026

Why Convert BMP to PNG?

BMP (Bitmap Image File) is one of the oldest image formats still in active use. Created by Microsoft in the 1980s for Windows, BMP stores raw, uncompressed pixel data — which means files are enormous. A single 1920×1080 screenshot saved as BMP weighs around 6 MB. A folder of 100 screenshots can consume over 600 MB before you have done anything useful with them.

PNG (Portable Network Graphics) solves this while keeping quality completely intact. Both BMP and PNG are lossless formats — no pixel data is discarded during conversion. The difference is efficiency: PNG's Deflate compression algorithm typically reduces file size by 60 to 80 percent compared to uncompressed BMP, with zero visual difference.

Converting BMP to PNG is the right choice when you need:

BMP to PNG is a fundamentally different conversion from BMP to JPG. When you convert BMP to JPG, you trade quality for size — JPG is lossy and permanently discards image data. When you convert BMP to PNG, you lose nothing: same quality, smaller file. It is always the right choice for screenshots, diagrams, text-heavy images, logos, and any image where crisp edges and accurate colors matter.

For a detailed breakdown of when PNG is the right target format, see our PNG vs JPG comparison guide.

Method 1: Convert BMP to PNG in Your Browser (No Upload Required)

The fastest, most private method is a browser-based converter that runs entirely on your device. PhotoFormatLab's BMP to PNG converter uses WebAssembly to process your files locally — your BMP images never leave your computer.

Step-by-step:

Why browser-based conversion matters for BMP files:

BMP files frequently contain screenshots, internal software exports, scanned documents, and legacy business data. Uploading these to server-based converters like Convertio or FreeConvert means your files transit over the internet and are temporarily stored on third-party infrastructure. Browser-based conversion eliminates this entirely.

For more on why browser-based conversion is the safer choice, read our guide on converting images without uploading to a server.

Method 2: Convert BMP to PNG on Mac with Preview

Mac users have a strong built-in option: Preview, macOS's default image viewer, handles BMP natively and exports to PNG directly.

Single File Conversion

Batch Conversion with Preview

Preview supports batch export for converting folders of BMP files at once:

Preview is reliable, produces correct lossless PNG output, and handles most standard BMP files without issues. Its main limitation is speed on very large batches — for hundreds of files, the CLI methods below are faster.

Method 3: Convert BMP to PNG on Windows

Windows has native BMP support baked in, making conversion straightforward without any extra software.

Using Microsoft Paint

Paint is the easiest single-file option:

Paint produces clean PNG output with no quality loss. The downside is no batch processing — repeat this process for each file.

Using Windows Photos App

Batch Conversion on Windows with IrfanView

For batch BMP to PNG conversion on Windows, IrfanView (free) is the best native tool:

IrfanView processes batches quickly and supports PNG compression level control, making it ideal for large BMP libraries.

Method 4: sips Command Line (macOS)

macOS includes sips (scriptable image processing system) as a built-in tool available on every Mac without any additional software.

Convert a single BMP file:

```bash

sips -s format png screenshot.bmp --out screenshot.png

```

Batch convert all BMP files in a folder:

```bash

for f in ~/Documents/bitmaps/*.bmp; do

sips -s format png "$f" --out "${f%.bmp}.png"

done

```

Batch convert to a separate output folder:

```bash

mkdir -p ~/Documents/png-output

for f in ~/Documents/bitmaps/*.bmp; do

basename=$(basename "$f" .bmp)

sips -s format png "$f" --out ~/Documents/png-output/"$basename".png

done

```

sips is fast, pre-installed, and ideal for macOS users who need to automate BMP to PNG conversion as part of a larger workflow. It handles standard 24-bit and 32-bit BMP files correctly.

Method 5: ImageMagick (Windows, Mac, Linux)

ImageMagick is an open-source cross-platform tool for batch image processing. Install via the ImageMagick website or on macOS via Homebrew (brew install imagemagick).

Convert a single file:

```bash

magick input.bmp output.png

```

Batch convert all BMP files in the current directory:

```bash

for file in *.bmp; do

magick "$file" "${file%.bmp}.png"

done

```

Batch with output to a separate folder:

```bash

mkdir -p png-output

for file in *.bmp; do

magick "$file" png-output/"${file%.bmp}.png"

done

```

Set PNG compression level (0–9, higher = smaller file, slower):

```bash

magick input.bmp -define png:compression-level=9 output.png

```

ImageMagick handles 16-bit BMP files, high-DPI BMP files from scanning software, and unusual BMP variants (BMP3, BMP4) that some other tools choke on. It is the most capable option for non-standard BMP inputs.

Python Pillow alternative:

For developers, Pillow handles BMP to PNG conversion cleanly:

```python

from PIL import Image

import os

def convert_bmp_to_png(input_path, output_path):

with Image.open(input_path) as img:

img.save(output_path, 'PNG', optimize=True)

# Batch convert all BMP files in a directory

for filename in os.listdir('./bmp_files'):

if filename.lower().endswith('.bmp'):

convert_bmp_to_png(

f'./bmp_files/{filename}',

f'./png_files/{filename.rsplit(".", 1)[0]}.png'

)

```

Pillow automatically handles the BMP color mode and produces clean PNG output. It integrates easily into image processing pipelines.

BMP vs PNG: Feature Comparison

Understanding the differences clarifies why PNG is almost always the better delivery format:

Key takeaways:

When Should You Convert BMP to PNG vs JPG?

Choosing the right output format matters:

Convert BMP to PNG when:

Convert BMP to JPG instead when:

For most BMP files — which are typically screenshots, scans, or software exports — PNG is the correct output format. The lossless upgrade keeps quality perfect while dramatically reducing file size. For photographic BMPs, BMP to WebP gives you the best of both worlds: smaller than JPG, better quality than JPG, and good web compatibility.

Understanding BMP Transparency During Conversion

Standard 24-bit BMP files have no alpha channel. If your BMP has a solid-color background (typically white, black, or magenta/cyan as a "chroma key"), converting it to PNG will preserve that solid background exactly — transparency is not automatically added.

If you want to make the background transparent in the resulting PNG, you will need an image editor (GIMP, Photoshop, Affinity Photo) to apply background removal after conversion. Browser-based tools like PhotoFormatLab convert the BMP faithfully; background removal is a separate editing step.

32-bit BMP files: Some Windows applications do save BMP files with an alpha channel embedded in the 32-bit format. When converting 32-bit BMP to PNG, ImageMagick and Pillow handle the alpha correctly. Preview on macOS and Paint on Windows may not preserve the alpha channel from 32-bit BMPs — use Method 1 (browser-based) or Method 5 (ImageMagick) if alpha preservation matters.

Frequently Asked Questions

Does converting BMP to PNG lose quality?

No. Both BMP and PNG are lossless formats. Converting BMP to PNG preserves every pixel exactly — no image data is discarded and no compression artifacts are introduced. The output PNG is visually identical to the source BMP. This is the key difference from converting BMP to JPG, which permanently discards image data through lossy compression. BMP to PNG is always a safe, lossless conversion.

How much smaller will my PNG file be compared to BMP?

Typically 60–80% smaller. A 6 MB BMP screenshot generally becomes 1 to 2 MB as PNG. The exact reduction depends on image content: screenshots with large flat-color areas compress very well, while complex photographic BMPs may compress less. PNG's Deflate algorithm is specifically optimized for images with repeating patterns, sharp edges, and flat areas — which is exactly what most BMP files contain.

Is it safe to convert BMP files online?

With PhotoFormatLab, yes — entirely safe. The conversion runs in your browser using WebAssembly; your BMP files never leave your device. Server-based converters like Convertio or FreeConvert upload your files to remote servers, which creates privacy risks for screenshots, scanned documents, or internal business graphics. Read our full breakdown of whether online converters are safe for a detailed comparison.

Can I convert multiple BMP files to PNG at once?

Yes. PhotoFormatLab supports batch conversion — select multiple BMP files at once and download all results as a ZIP. On macOS, Preview's "Export Selected Images" feature handles batches natively. For large batches or automation, sips (macOS) and IrfanView (Windows) are the fastest options. ImageMagick and Python Pillow are ideal for scripted pipelines.

Why does my PNG file look identical to the BMP but take up less space?

BMP stores pixel data with no compression (or only simple run-length encoding). PNG applies Deflate lossless compression — a sophisticated algorithm that identifies and compresses repeating patterns without discarding any data. The decompressed PNG and the original BMP produce the exact same pixels, but the compressed file on disk is much smaller. No quality is lost; only storage space is recovered.

Should I use PNG or WebP for web images converted from BMP?

WebP is usually better for web delivery. WebP supports lossless compression (like PNG) but produces files roughly 25–35% smaller than equivalent PNG at the same quality. If you are converting BMP files specifically for use on a website, BMP to WebP is worth considering for better page speed. PNG remains the better choice for design files, files you will edit further, or situations where maximum compatibility matters (legacy browsers or design tools with limited WebP support).