CMYK Converter (print color to RGB and hex)

CMYK and RGB

Screens and printers build color in opposite ways. RGB isadditive: start from black and add red, green, and blue light until you reach white. CMYK is subtractive: start from white paper and add cyan, magenta, yellow, and black ink, each absorbing light until you reach black.

K = 1 − max(R, G, B)  ·  C = (1 − R − K) / (1 − K)

Why there's a separate black

In theory equal amounts of cyan, magenta, and yellow make black. In practice they make a muddy brown, use three times the ink, and soak the paper. Printers therefore add a dedicated black plate — the "K", for key — which gives crisp text, deeper blacks, and lower cost.

The conversion is only an approximation

This is the important caveat: there is no single correct RGB↔CMYK conversion. The result depends on the specific inks, paper, and press profile, which is why professional workflows use ICC color profiles rather than a formula. Worse, the two gamuts don't overlap — vivid screen colors like bright cyan or intense orange simply cannot be printed, and print will substitute the nearest achievable color. Expect printed output to look slightly duller than your screen.

Worked example

#3B82F6 converts to roughly C 76, M 47, Y 0, K 4 — heavy on cyan and magenta with no yellow, which is what makes it blue. Converting back gives a very close but not always identical hex, since CMYK values are rounded to whole percentages.