Convert an image to grayscale
Turn a colour photo or graphic into shades of grey in a local browser worker. The pixels are rewritten on your device, so nothing is uploaded.
Processing locally…
Your image is ready
Image to grayscale in three steps
Converting a photo to grayscale sounds like removing colour, and it is, but the way the colour is removed decides how the picture looks. The simplest method averages the red, green and blue values of each pixel. That treats the three as equally bright, and they are not: the eye is far more sensitive to green than to blue, so a plain average makes a blue sky look too light and a green leaf too dark.
This tool weights the channels instead. Each pixel’s grey is 21% of its red, 72% of its green and 7% of its blue, which are the Rec. 709 luma coefficients and the same weights the CSS grayscale filter uses. The result is a grey picture whose light and dark areas sit where they do in the colour original, which is what most people mean by a good black and white conversion.
What stays the same
The width and height are unchanged, and so is the shape of everything in the picture. Only the colour of each pixel is rewritten. Transparency is left alone, so a PNG logo on a transparent background stays on a transparent background, and its edges are not touched.
What changes
The colour is gone, and it cannot be recovered from the grey file. A JPG is encoded again when it is saved, so a small amount of quality is lost, as it is with any JPG edit. Starting from a PNG or WebP avoids that. A browser cannot write AVIF, so an AVIF photo is saved as a WebP instead. If you may want the colour later, keep the original file.
When grayscale is useful
Grayscale is often the right choice for a document scan that will be printed on a black and white printer, for a photo that will sit inside a design that uses no colour, or for a picture where colour distracts from the shapes.
For a PDF instead of a single image, use Grayscale PDF, which converts the colours inside a document while keeping its text as text.
Many images, one setting
Up to twenty images can be handed over at once and the same conversion applied to each. They run one at a time, and each gets its own row and its own download. A file that cannot be read loses only itself, and the rest are finished.
Nothing leaves the device
The image is read and rewritten by a worker inside your browser. There is no upload, no account and no server copy, so a personal photo does not have to be handed to anyone to be turned grey.
- 1
Choose a supported image
- 2
Convert it to grayscale
- 3
Preview and download the result
Frequently asked questions
How is each grey chosen?
Red, green and blue are weighted 21%, 72% and 7% of the value, the same weights the CSS grayscale filter uses. Green counts most because the eye is most sensitive to it.
Does it keep the size and transparency?
Yes. The width and height do not change, and a transparent area of a PNG or WebP stays transparent, because only the colour channels are rewritten.
Can I turn the colour back on afterwards?
No. The grey file no longer holds the colour, so keep the original if you may want it. Nothing is stored here, so the only copy of the colour is the file you started with.
Can I convert several images at once?
Yes, up to twenty at a time with the same result for each. They run one after another, and each gets its own download.
Does FileGizmo store the image?
No. The source and the output stay inside your browser session, and nothing is uploaded.