CMYK Color Converter
Convert between CMYK (the subtractive cyan/magenta/yellow/key model used by printers) and RGB / HEX / HSL (the additive model used by screens). Given RGB, the black (key) channel is K = 1 − max(R,G,B) and the color channels are C = (1−R−K)/(1−K) (likewise M, Y) — so pure red (#FF0000) becomes CMYK 0,100,100,0 and black becomes 0,0,0,100. The inverse is R = 255·(1−C)·(1−K). Enter any representation to get the others with a live swatch, plus the eight process-color corners. Note these are the idealized mathematical conversions — real press CMYK depends on an ICC profile and dot gain, so on-screen CMYK is an approximation. Everything runs locally in your browser.
RGB (0–255)
CMYK (0–100%)
Result
Process-color corners
The math. CMYK is subtractive: inks subtract light, so more ink means a darker color, the opposite of additive RGB. To convert RGB (each channel 0–1) to CMYK, first find the key (black) channel K = 1 − max(R,G,B); this is the amount of black ink that can replace an equal mix of the three color inks. Then the remaining color is C = (1 − R − K) / (1 − K), M = (1 − G − K) / (1 − K), Y = (1 − B − K) / (1 − K) (when K = 1, i.e. pure black, C = M = Y = 0 to avoid division by zero). Converting back: R = (1 − C)·(1 − K), G = (1 − M)·(1 − K), B = (1 − Y)·(1 − K), scaled to 0–255. White (#FFFFFF) maps to 0,0,0,0 (no ink) and black (#000000) to 0,0,0,100 (key only); the three RGB primaries each become the complementary two-ink mix (red → 0,100,100,0). HSL is derived from RGB. Bear in mind this is the idealized formula — real CMYK is device-dependent (ICC profile, dot gain, ink limits, "rich black" mixing K with CMY), so two presses can reproduce different colors from the same CMYK numbers. Pairs with the Color Converter (HEX/RGB/HSL), OKLCH Converter, and Color Temperature → RGB tools. Everything runs locally — nothing leaves your browser.