RGB to CMYK Converter

Convert an on-screen RGB color into CMYK print percentages instantly. Enter the Red, Green, and Blue channels (each 0–255) and the tool returns the four CMYK ink values — Cyan, Magenta, Yellow, and Key/Black — as percentages from 0 to 100%, alongside the hex code and a live color swatch so you can see exactly what you are converting.

RGB is an additive model built for light-emitting screens, where full intensity of every channel produces white. CMYK is a subtractive model built for printing, where inks absorb light and stacking all of them approaches black. Because the two models describe color in opposite ways, any design headed for physical print — business cards, flyers, packaging, posters — needs its screen colors translated to CMYK first.

How to use it

1. Type a value into each of the R, G, and B fields (0–255).
2. Read the CMYK result, formatted as cmyk(c%, m%, y%, k%).
3. Copy the CMYK or HEX string, or download the full breakdown table as a CSV.

The conversion runs entirely in your browser as you type — nothing is uploaded to a server.

How the conversion works

The tool uses the standard mathematical RGB→CMYK formula. Each channel is normalized to a 0–1 range, the black (Key) component is taken from the brightest channel, and the remaining ink amounts are derived from it:

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)

Pure black (0, 0, 0) is a special case: K becomes 100% and C/M/Y are all 0%, avoiding a division by zero.

Why do my printed colors look different?

This is a device-independent mathematical conversion, not a color-managed one. Real presses reproduce color through ICC profiles tuned to a specific ink set, paper stock, and press condition (for example U.S. Web Coated SWOP or FOGRA39). Highly saturated RGB colors — bright cyans, greens, and oranges — often sit outside the printable CMYK gamut, so they will appear duller or shifted on paper. For proofing that must match a print run exactly, do the final separation in Adobe Photoshop, Illustrator, or a RIP with the correct output profile. Use this converter for quick estimates, CSS-to-print mapping, and getting into the right ballpark.

What does the K in CMYK stand for?

K is the Key channel — black ink. It is called "Key" (rather than "B", which would collide with Blue) because in traditional four-color printing the black plate carries the key detail and alignment that the other plates register against. Adding a dedicated black ink is also cheaper and sharper than building black from full cyan, magenta, and yellow.

Is this the same as converting HEX to CMYK?

Yes. A hex color such as #FF6600 is just RGB written in base-16 (FF=255, 66=102, 00=0), so converting hex to CMYK is identical — expand the hex to its R, G, B values and run the same formula. This tool shows the hex code beside the CMYK result for exactly that reason.