Convert RGB to CMYK
This RGB to CMYK converter translates on-screen red, green and blue values into cyan, magenta, yellow and black percentages. Use it to get approximate ink values for a flyer, business card or print brief when all you have is an RGB color from a website or a design file.
Additive versus subtractive color
RGB is additive: a screen starts black and adds light, so 255, 255, 255 is white. CMYK is subtractive: paper starts white and each ink removes part of the light, so more ink means a darker result. In theory full cyan, magenta and yellow make black; in practice they make a muddy brown, which is why printers add a separate black ink (K).
The formula and a worked example
R' = R/255 G' = G/255 B' = B/255
K = 1 − max(R', G', B')
C = (1 − R' − K) / (1 − K)
M = (1 − G' − K) / (1 − K)
Y = (1 − B' − K) / (1 − K)For a burnt orange, rgb(234, 88, 12):
R' = 0.9176 G' = 0.3451 B' = 0.0471
K = 1 − 0.9176 = 0.0824 → 8.2%
C = (1 − 0.9176 − 0.0824) / 0.9176 = 0 → 0%
M = (1 − 0.3451 − 0.0824) / 0.9176 = 0.6239 → 62.4%
Y = (1 − 0.0471 − 0.0824) / 0.9176 = 0.9487 → 94.9%
→ cmyk(0%, 62.4%, 94.9%, 8.2%)A second example shows how darkness is handled: teal rgb(0, 128, 128) becomes cmyk(100%, 0%, 0%, 49.8%). All of the darkening goes into K, and cyan alone carries the hue.
Limits of the simple formula
This textbook formula is handy for estimates, comparisons and learning, but it is not a color-managed conversion. Real separations are made with ICC profiles for a specific press, ink and paper, and they differ in several ways:
- Black generation. The formula moves the entire grey component into K, so one of C, M or Y is always 0. Press profiles usually use less black and more colored ink in darker tones.
- Total ink limits. Presses cap the combined ink coverage. Profiles respect that limit; the formula doesn't know about it.
- Gamut. Many bright RGB colors, especially saturated blues, greens and oranges, can't be reproduced with process inks. The formula still returns numbers, but the print will look duller.
- Rich black.
rgb(0, 0, 0)becomescmyk(0%, 0%, 0%, 100%). For large black areas, designers often add some cyan, magenta and yellow for a deeper "rich black"; ask your printer what they recommend.
Treat the result as a first draft, and for final artwork convert in a color-managed application using your printer's profile. Alpha values in the input are ignored; semi-transparent colors are covered in RGBA to CMYK. Starting from a hex code? Use HEX to CMYK. To preview CMYK numbers on screen, try CMYK to RGB.