What Is the RGB to CMYK Converter?
This tool converts colors from the RGB model (Red, Green, Blue — used on screens and digital displays) to the CMYK model (Cyan, Magenta, Yellow, Key/Black — used in printing). RGB is an additive model based on emitted light, while CMYK is a subtractive model based on reflected light from ink on paper. Designers regularly convert between the two when preparing artwork for print.
How to Use It
Enter your Red, Green, and Blue values, each ranging from 0 to 255. Submit the form and you'll instantly get the equivalent CMYK percentages (0–100% for each channel). Values outside 0–255 are automatically clamped to the valid range.
The Formula Explained
First, each RGB channel is normalized to a 0–1 range by dividing by 255: \(R' = R/255\), \(G' = G/255\), \(B' = B/255\). The black key channel is \(K = 1 - \max(R', G', B')\). The remaining channels are then
$$C = \frac{1-R'-K}{1-K}, \quad M = \frac{1-G'-K}{1-K}, \quad Y = \frac{1-B'-K}{1-K}$$When the color is pure black (\(R=G=B=0\)), \(K\) equals 1 and \(C\), \(M\), \(Y\) are set to 0 to avoid division by zero.
Worked Example
Take the "Tomato" color RGB(255, 99, 71). Normalized: \(R'=1\), \(G'=0.388\), \(B'=0.278\). Since the max is 1, \(K = 1 - 1 = 0\). Then
$$C = \frac{1 - 1 - 0}{1 - 0} = 0\%, \quad M = \frac{1 - 0.388}{1} = 61.18\%, \quad Y = \frac{1 - 0.278}{1} = 72.16\%$$So the CMYK is approximately (0%, 61.18%, 72.16%, 0%).
FAQ
Why does my printed color look different? CMYK has a smaller color gamut than RGB, so vivid screen colors (especially bright greens and blues) often appear duller in print. This converter uses the standard mathematical conversion, not an ICC color-managed profile.
What does K stand for? K is the "Key" plate, which in practice is black ink. It's called "Key" because the other plates are aligned (keyed) to it.
What CMYK does pure white give? RGB(255,255,255) produces 0% for all four CMYK channels — no ink at all, leaving the white paper.
