Image Grayscale Converter
Grayscale is more than removing color: how each channel is weighted decides whether the result looks natural or muddy.
How to use
- Drop a PNG, JPG or WebP into the upload area.
- Optionally raise the contrast slider to add punch (0 keeps the plain grayscale).
- Choose PNG to keep transparency, or JPG for a smaller file.
- Download the black-and-white result.
Frequently asked questions
Which grayscale formula do you use?
The standard Rec. 709 luminance weights — 0.2126 red, 0.7152 green and 0.0722 blue — the same coefficients our contrast checker uses for relative luminance. These weights are applied directly to the sRGB channel values without gamma linearization (our contrast checker linearizes before weighting), so the result approximates rather than exactly equals WCAG relative luminance. Green dominates because human eyes are most sensitive to it, which keeps results looking natural.
What does the contrast slider do?
It stretches the gray tones away from mid-gray, by up to twice at 100%. It is applied after the color removal and helps flat-looking scans and screenshots regain punch. At 0 nothing is changed beyond the grayscale itself.
Will transparency survive?
Yes, when you output PNG: the alpha channel is untouched and only the colors turn gray. JPG has no transparency, so transparent areas are composited onto white.
Why is the result different from a simple average?
A naive (R+G+B)/3 treats every channel equally and usually makes greens and skin tones too dark. The weighted formula follows human brightness perception instead, which is why it is the industry standard.
Are my images uploaded anywhere?
No. The pixels are processed in your browser on your own device; nothing is transmitted, stored or logged.
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About this tool
Grayscale is more than removing color: how each channel is weighted decides whether the result looks natural or muddy. This tool converts any PNG, JPG or WebP to black-and-white using the same luminance weights as our contrast checker — 0.2126 red, 0.7152 green, 0.0722 blue, the standard Rec. 709 coefficients, a brightness approximation weighted by human-eye sensitivity. Green counts far more than blue, which is why naive averaging makes foliage and skin tones look wrong. An optional contrast slider stretches the gray tones away from mid-gray by up to twice at maximum, useful for scans and screenshots that come out flat; at zero nothing changes beyond the color removal. Transparency is preserved when you output PNG, or you can export a compact JPG for photos. Every pixel is processed in your browser — no upload, no account, no watermark — and the original on your disk stays untouched. Drop an image in, adjust the slider if you like, and download the result.