Guide
CMYK Colors Explained
CMYK is the color model used in printing. It describes how much cyan, magenta, yellow and black ink to lay down on paper. A screen color converted to CMYK is a useful starting point, but it is not a promise of how the print will look.
What CMYK is
CMYK stands for cyan, magenta, yellow and key. The key plate is black, which is why the last letter is K and not B. Each value is a percentage of ink from 0% to 100%. Printed inks absorb light, so this model is called subtractive: more ink makes the result darker. That is the opposite of how RGB screens add light.
- Cyan absorbs red light.
- Magenta absorbs green light.
- Yellow absorbs blue light.
- Black adds depth and keeps small text and fine lines sharp, so it is not left to a mix of the other three.
Converting RGB to CMYK
The simple conversion used on this site starts from the strongest RGB channel. Write each channel as a fraction of 255, then:
- K = 1 − the largest of R, G and B.
- C = (1 − R − K) ÷ (1 − K), and the same with G for M and with B for Y.
- Multiply each result by 100 to get a percentage.
For royal blue, #4169E1, the channels are 0.255, 0.412 and 0.882. K = 1 − 0.882 = 12%, C = 71%, M = 53% and Y = 0%, so the CMYK value is cmyk(71%, 53%, 0%, 12%). A few more examples:
| Color | HEX | C | M | Y | K |
|---|---|---|---|---|---|
| Red | #FF0000 | 0 | 100 | 100 | 0 |
| Lime | #00FF00 | 100 | 0 | 100 | 0 |
| Blue | #0000FF | 100 | 100 | 0 | 0 |
| Yellow | #FFFF00 | 0 | 0 | 100 | 0 |
| Gray | #808080 | 0 | 0 | 0 | 50 |
| Royal Blue | #4169E1 | 71 | 53 | 0 | 12 |
| Black | #000000 | 0 | 0 | 0 | 100 |
You can convert any color with the HEX to CMYK converter. Every color page on this site also lists its CMYK value.
Why prints look different from screens
This formula is pure arithmetic. It knows nothing about the paper, the inks or the press, and those decide the real result. A few reasons a printed color can differ from the screen:
- Different ranges. A screen can show some very saturated colors, especially bright cyans, greens and oranges, that CMYK inks cannot reproduce. Those colors print duller.
- Different light. A screen makes its own light. Paper reflects the light in the room, so the same print looks different under daylight and under warm indoor bulbs.
- Different paper. Coated and uncoated stock absorb ink differently. The same CMYK values look brighter on glossy paper than on newsprint.
- Different profiles. Professional print work uses an ICC color profile for the press and paper. The simple formula above does not.
Rule of thumb: use the CMYK numbers here as a reference, then ask your printer for their color profile or a printed proof before an important job. Design software can apply that profile and show a closer preview.
The K channel and rich black
Pure black converts to cmyk(0%, 0%, 0%, 100%), which uses only the black ink. That is the right choice for body text, because a single ink cannot go out of register. For large black areas, printers often use rich black, which adds some cyan, magenta and yellow under the black for a deeper result. Print shops limit the total amount of ink on the paper, so ask which rich black mix they recommend rather than inventing one.
Spot colors
Brand colors are often specified as spot colors, such as a Pantone color, which are mixed as a single special ink instead of built from four. A CMYK number for such a color is an approximation. If an exact brand color matters in print, ask for the spot ink or the official CMYK recipe from the brand's guidelines.
A short checklist for print work
- Design in the color mode your printer asks for, usually CMYK for ink on paper.
- Ask the printer for their color profile and the maximum total ink coverage.
- Keep body text as pure black ink on a light background.
- Expect very bright screen colors to print duller, and choose slightly deeper colors when you can.
- Order a proof for anything where a color must match exactly.