RGB to CMYK Converter

Normalize each RGB channel to 0-1 by dividing by 255. Then K = 1 - max(R', G', B'). If K = 1 the color is pure black and C, M, Y are all 0. Otherwise C = (1 - R' - K) / (1 - K), M = (1 - G' - K) / (1 - K), and Y = (1 - B' - K) / (1 - K). Multiply each by 100 to get the standard 0-100 percentage output.

Use R = 255 x (1 - C/100) x (1 - K/100), G = 255 x (1 - M/100) x (1 - K/100), and B = 255 x (1 - Y/100) x (1 - K/100). The result is rounded to whole 0-255 values. Round-tripping a value (RGB to CMYK and back) usually returns the same color, with at most a one-unit rounding drift on each channel.

Not necessarily. This converter applies an uncalibrated channel formula and does not use source or destination color profiles. A production conversion needs the correct ICC profiles for the display space, press, ink, and paper. Use this result as an estimate, then proof with the print provider's specified profile.

In theory, equal amounts of cyan, magenta, and yellow make black. In practice, mixing inks produces a muddy dark brown and wastes ink. Adding a dedicated black channel (K, the 'key' plate) gives sharper text, deeper blacks, and lower ink usage. K is derived as 1 minus the largest normalized RGB channel, which is the maximum amount of black you can pull out without changing the hue.

Each RGB channel must be a whole number from 0 to 255, and each CMYK channel must be 0 to 100. Negative numbers, values above the maximum, and non-numeric input (including blank fields or text) are rejected and the converter shows an error instead of a guessed result.