Screen color versus print color
RGB is an additive model: screens start from black and add red, green and blue light to make a color. CMYK is a subtractive model: printing starts from white paper and adds cyan, magenta, yellow and black ink, which absorb light.
The conversion uses a standard formula. The black (K) value is 1 minus the brightest RGB channel, and cyan, magenta and yellow are then calculated from what is left, all expressed as percentages. For rgb(255, 128, 0) the brightest channel is full, so K is 0%. Green is about half, so magenta comes out at 50%, red is full so cyan is 0%, and blue is 0 so yellow is 100%. The result is cmyk(0%, 50%, 100%, 0%).
This is a mathematical conversion, not a color-managed one, so it does not account for paper, ink or press profiles.
When you would convert RGB to CMYK
You usually need CMYK numbers when a brand color defined for screen has to appear on printed material: business cards, packaging, brochures or signage. Some print order forms, label templates and older design workflows ask for CMYK percentages directly.
It is also useful to preview roughly how much ink a color calls for. Very vivid blues and greens that look striking on screen often shift when printed, because inks cannot reproduce every color a display can.
If your color starts as a HEX code, first split it with the HEX to RGB converter and then enter the three numbers here.
How to convert RGB to CMYK with this tool
- Enter the red, green and blue values in the R, G and B boxes. They start at 91, 79 and 240.
- Use whole numbers from 0 to 255.
- Read the result underneath, shown as cmyk(c%, m%, y%, k%).
- Use the swatch on the right to confirm the color you typed, then copy the CMYK values by selecting the text.
The result updates as you type, and everything runs locally in your browser. The swatch shows the RGB color on your screen, not a simulation of ink on paper.
Cautions before sending a color to print
Treat the numbers as a starting point and always request a printed proof for anything important. Two printers can reproduce identical CMYK values slightly differently, and the same file looks different on coated and uncoated paper.
Each percentage is rounded to a whole number. Pure black rgb(0, 0, 0) returns cmyk(0%, 0%, 0%, 100%), which uses black ink only. Some print specialists prefer a richer black built from several inks, and this tool does not offer that.
The tool does not clamp the inputs, so values outside 0 to 255 can give percentages below 0 or above 100. Keep to the valid range. For a full set of notations in one view, try the color converter.