⚫ Grayscale Converter
Drag and drop an image, or click to select one
Convert an uploaded image to grayscale. Choose from three conversion methods: "luminosity" (weighted for human eye sensitivity), "average" (a simple mean of the RGB values), or "lightness" (the midpoint between the max and min channel values). Useful for a retro photo effect or previewing how an image will look in black and white before printing.
How to use
- Drag and drop an image, or click to select a file.
- Choose a conversion method (luminosity, average, or lightness).
- Press "Apply" to see a preview, then "Download" to save it.
How the calculation works
Convert a colour image to greyscale, choosing one of three methods. Luminosity: 0.299 × red + 0.587 × green + 0.114 × blue Our eyes are most sensitive to green and least to blue, so this weights the channels accordingly (the same coefficients as the ITU-R BT.601 television standard). It gives the most natural brightness. Average: (red + green + blue) ÷ 3 Lightness: (highest channel + lowest channel) ÷ 2 PNG images are saved as PNG; others as JPEG at 92% quality.
Worked example
Pure blue (red 0, green 0, blue 255) Luminosity: 0.114 × 255 ≈ 29 (quite dark grey) Average: 255 ÷ 3 = 85 Lightness: (255 + 0) ÷ 2 ≈ 128 (mid grey) With luminosity, blue, which looks dark to us, becomes a dark grey, which looks natural.
Things to be aware of
- Colours of similar brightness, such as red text on green, become hard to tell apart in greyscale. Check before printing in black and white.
- For black-and-white photos, a little extra contrast after converting adds punch.
- Processing happens in your browser; the image is never uploaded.
FAQ
What's the difference between the three methods?
"Luminosity" is a weighted calculation that accounts for the human eye's higher sensitivity to green, giving the most natural-looking result. "Average" takes a simple mean of the RGB values, which can look a bit flat. "Lightness" takes the midpoint between the highest and lowest channel values, which tends to produce stronger contrast.
Not sure which method to pick?
"Luminosity" is recommended if you're unsure — it gives the most natural-looking result in most cases.
Is my uploaded image sent to a server?
No, all processing happens entirely in your browser.