Grayscale Converter — Make a Black-and-White Photo
Last updated: 2026-06-25
Photos never leave your device · 100% client-sideGrayscale conversion removes the color from a photo, keeping only the brightness to turn it black and white.
This tool uses the luminance formula (0.299R + 0.587G + 0.114B) for a natural black-and-white, all processed on a canvas in your browser.
Grayscale Tool
How to use
- Select an image — Drag the photo you want to convert, or upload it with the file picker.
- Adjust strength — Use the grayscale strength slider (0–100%) to set how much color to remove. 100% is fully black and white.
- Check the preview — Confirm the grayscale result in the canvas preview.
- Download — Click the download button to save the black-and-white image.
How grayscale works (the luminance formula)
Grayscale conversion merges a color pixel's red (R), green (G) and blue (B) values into a single gray brightness. A plain average of the three diverges from how bright we actually perceive a color and looks off. So we use luminance weights that reflect how the eye is most sensitive to green and least to blue.
gray = 0.299 × R + 0.587 × G + 0.114 × B
The strength slider blends this gray value with the original color. At 100% you get full black and white, at 50% a half-desaturated faded look, and at 0% the original color is untouched.
Grayscale methods compared
| Method | Calculation | Character |
|---|---|---|
| Luminance weights (this tool) | 0.299R + 0.587G + 0.114B | Most natural to the eye |
| Simple average | (R + G + B) / 3 | Easy but distorts brightness |
| Desaturation | HSL with S = 0 | Removes color, keeps lightness |
After converting to grayscale, use image compression to cut size, or resize image to change dimensions. For format choice, see the WebP vs JPG vs PNG guide.
Frequently asked questions (FAQ)
How is the grayscale conversion calculated?
Each pixel's red, green and blue (RGB) values are combined into a single gray brightness using weights tuned to the eye's sensitivity (0.299R + 0.587G + 0.114B). This luminance method produces a more natural black-and-white than a simple average.
Can I adjust the grayscale strength?
Yes. The strength slider goes from 0 to 100%. At 50% you get a faded look (desaturation) that is half color, half gray, and at 100% the image is fully black and white.
Does converting to grayscale reduce file size?
PNG and WebP can get somewhat smaller because the color information is simpler. For bigger savings, follow up grayscale conversion with image compression.
Are my photos uploaded to a server?
No. Grayscale conversion runs 100% inside your browser, and your photos are never uploaded or stored.
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Last updated: 2026-06-25