Grayscale Converter

This free online grayscale image converter turns colour photos into black and white in your browser — nothing is uploaded. Drag the Intensity slider to control how much desaturation to apply: 100% for a full monochrome result, or lower values for a muted, partially desaturated look. The output preserves your original format and shows the file size so you can download with confidence.

How to use

1. Drop a JPG, PNG, or WebP image into the upload zone.
2. Adjust the Intensity slider (0–100%) — 100% is fully black and white.
3. Click Apply to process the image.
4. Preview the result and check the output file size.
5. Click Download to save your grayscale image.

Why grayscale isn't just the average of R, G and B

The obvious approach — add the three channels and divide by three — produces flat, muddy results, because human vision is not equally sensitive to each primary. We perceive green as far brighter than blue at the same numeric value, so averaging makes greens too dark and blues too light.

Correct conversion uses luminance weighting, roughly 21% red, 72% green, and 7% blue. Green dominates because that is where the eye is most sensitive; blue contributes least. The visible difference is largest exactly where it matters — foliage, skies, and skin tones — which is why a properly weighted conversion keeps contrast that a naive average destroys.

Why your phone's black-and-white mode looks different

Because a camera's monochrome mode is not only removing colour. It typically applies a tone curve as well — deepening blacks, lifting highlights, and adding contrast to imitate black-and-white film, which had a much steeper response than a digital sensor. A straight luminance conversion is the neutral, faithful version of the image, and it will look flatter by comparison. If you want the punchier look, run the result through the brightness and contrast tool afterwards.

Partial desaturation

The intensity slider blends between the original and the fully desaturated version, so 100% is true grayscale and intermediate values keep some colour. This is more useful than it first appears: 60–80% desaturation mutes distracting colour while leaving enough to distinguish elements, which suits background imagery sitting behind text, and gives a period look without the starkness of full monochrome.

It usually won't shrink the file much

Removing colour does not remove colour channels. The output is still an RGB image in which the three channels happen to hold equal values, so the format stores the same amount of data. JPEG and WebP typically shrink somewhat because there is less chroma variation to encode, but the saving is modest. To actually reduce size, use the image compressor.