8-Bit Grayscale BMP Converter
Winzerk converts images to uncompressed 8-bit grayscale BMP directly in your browser. Prepare files for software or equipment that requires a grayscale bitmap, with optional resizing to specific pixel dimensions.
Use the converter on the homepage. No account, installer, or image upload is required.
How to export an 8-bit grayscale BMP
- Open the Winzerk image converter and choose or drop your images.
- Choose BMP under Convert all to.
- Leave BMP color set to 8-bit grayscale (default).
- If needed, enable Resize images and enter your dimensions.
- Select Convert All, then download individual files or use Download All as ZIP for the batch.
Supported source formats include JPG/JPEG, PNG, WebP, HEIC/HEIF, and BMP.
What is an 8-bit grayscale BMP?
Each pixel in an 8-bit BMP stores a one-byte index into a color palette. An 8-bit BMP can have a color palette; it is not automatically grayscale. Winzerk writes a palette of 256 gray values, from black to white, so every pixel refers to a shade of gray.
The output is uncompressed BMP with a 40-byte Windows bitmap information header, a 256-entry grayscale palette, and bottom-up pixel rows padded to a multiple of four bytes. Color is converted to gray using a weighted combination of red, green, and blue values.
8-bit grayscale versus 24-bit color BMP
8-bit grayscale BMP stores one palette index per pixel and represents up to 256 shades of gray. 24-bit color BMP stores three color-channel bytes per pixel and retains color. Winzerk offers both options in the BMP color control.
The grayscale pixel data uses one third as many bytes before row padding, but total file size also includes headers and the palette. Neither option uses image compression. Choose the bit depth required by the application receiving the file.
When is grayscale BMP useful?
Some legacy software, industrial tools, and image-processing workflows expect an uncompressed bitmap with a specific bit depth and size. Grayscale BMP can be useful for importing test images into machine-vision software, comparing intensity patterns, or preparing files for systems that do not accept newer image formats.
Check your target system's requirements for dimensions, palette, and BMP header support. An 8-bit grayscale export is not a 1-bit black-and-white image, a raw sensor file, or a calibrated measurement. Converting a photograph does not recover sensor data or guarantee compatibility with every machine.
Resize to exact dimensions
Enable resizing and choose Exact dimensions when your software requires a fixed width and height. Both values are required. This mode can enlarge images and intentionally stretch them if the chosen aspect ratio differs from the source.
Use Keep proportions / maximum dimensions to fit an image within size limits while preserving its aspect ratio. That mode does not enlarge smaller images.
Smooth or nearest-pixel resizing?
Smooth blends neighboring pixels during resizing and is generally suitable for photographs. Interpolation can introduce intermediate gray values around edges.
Nearest pixel disables canvas image smoothing. It avoids blending during resizing and is useful for pixel art, discrete patterns, or inspection images where crisp boundaries matter. It can look blocky when enlarged. Grayscale conversion still changes color values, and downscaling can discard detail.
Transparency and local processing
BMP exports from Winzerk do not retain transparency. Transparent areas become white, and partially transparent pixels are blended onto a white background before export.
Your image files are processed locally in your browser and are not uploaded for conversion. HEIC/HEIF decoding also happens locally. The website itself loads normally from its host; see the privacy page for details.