FineDocs
English

Turn a picture black and white

Make any photo greyscale in your browser, free and with no account. Pick the weighting film and photo editors use, or the flat average a naive filter gives.

Drop files here (up to 50)

or paste from the clipboard

Preview

Choose an image and the result appears here as you change the options.

Shows the framing and geometry exactly. Compression quality is not simulated.

Options

Weighted is what film and photo editors mean by monochrome. The average is what a naive filter does, and gives a flatter, older look.

%

Only applies to JPEG inputs. PNG and WebP are written back as PNG with nothing spent.

Results appear here. Nothing is uploaded.

    How it works

    Each pixel's three colour channels are collapsed into one number and that number is written back into all three, which is what a grey pixel is. The weighted setting uses the Rec. 601 coefficients — red counts for 0.299, green for 0.587 and blue for 0.114 — because the eye is far more sensitive to green light than to blue. The flat average treats all three equally instead. The alpha channel is never touched, so transparency survives exactly as it was.

    What to watch out for

    A grey file is rarely a smaller file

    The picture still has three colour channels, all now carrying the same values, so a JPEG or a PNG comes back roughly the size it went in and occasionally larger. Making a file smaller is a job for a compressor, and the compression tools on this site will do noticeably better on an image that has already been through this one.

    Two greens that look different in colour can come out identical

    Any conversion to grey throws information away, and pixels that differ in hue but match in brightness end up as the same shade. A red logo on a green background can vanish entirely. If two elements need to stay distinct, adjust the contrast before removing the colour rather than after.

    The change is permanent in the file that comes back

    There is no colour information kept in reserve and no way to reverse the conversion from the result. Keep the original if the colour version might ever be wanted, which is worth saying because the greyscale file has the same name as the one that went in.

    Limits

    Files up to about 50 MB work reliably. Beyond that, the ceiling is your device's memory rather than any rule we impose — the work happens on your own machine. Tested in Chrome 140, Firefox 143, Safari 18.

    The two ways to throw colour away

    Ask three programs to make a picture black and white and you can get three different pictures. The reason is that “grey” is not one operation.

    The obvious approach adds the red, green and blue values and divides by three. It is easy to explain and it is what most quick filters do, but it is wrong about how eyes work. Human vision is dominated by the green part of the spectrum: a pure green square looks far brighter than a pure blue one of the same numerical value. Treating the three channels equally makes greens too dark and blues too light.

    The weighted setting uses the coefficients broadcast television settled on when colour signals had to remain watchable on black-and-white sets. Green counts for roughly seven times what blue does. The result matches what the eye reports, and it is what any photo editor means when it says monochrome.

    Both are offered because the flat average is not merely a mistake. It produces a harder, older look that people sometimes want on purpose.

    What happens to transparency

    A PNG with a transparent background keeps it. Only the colour channels are rewritten; the alpha channel is copied through untouched, because transparency is not colour and has nothing to contribute to brightness.

    A JPEG has no transparency to keep, so anything transparent in a source that had it is filled with white before the conversion, which is the same rule the rest of this site follows.

    Nothing is uploaded

    The pixels are read and rewritten by a Web Worker inside this tab, on your own processor. Fifty files can be converted at once, none of them leaves the machine, and there is no daily limit because there is no server bill for anyone to recover.

    Your files never leave your browser. Last updated 2026-08-07.