RGB to CMYK Converter — Free, for Print

Screen colors don't print the way they look

RGB—the color model for screens—maps to CMYK—the ink model for printers—through a mathematical conversion. This tool applies the pure arithmetic: divide RGB values by 255, compute the black (K) component as whatever light is missing from the brightest channel, then derive cyan, magenta and yellow from what remains. All four outputs round to whole percentages.

Black is the first place it breaks

Pure black, rgb(0,0,0), converts here to cmyk(0%, 0%, 0%, 100%): all K, nothing else. Press work usually wants a rich black built with additional CMY underneath—a common recipe is cmyk(60%, 40%, 40%, 100%)—because K-only black looks washed out and slightly grey across large solid areas.

Note what a real rich black is not: adding 100% of all four inks gives 400% total coverage, which is registration black, used for crop and registration marks and never for printing an area. Presses impose a total ink limit, commonly around 240–300% depending on paper and press, and exceeding it causes the sheet to stop drying properly—ink offsets onto the next sheet, or the stock cockles and tears. The 60/40/40/100 recipe above lands at 240% for exactly this reason. This tool knows none of that: it has no print condition, so it can neither build a rich black nor warn you about ink limits.

Vivid screen colors fall outside the printable range

Bright greens, saturated oranges and other vivid screen colors simply cannot be reproduced by CMYK inks. The arithmetic still returns a number—and it looks fine on your monitor—but the printed result will be duller than expected. The conversion shows no warning because the number is technically valid; the limit is in the inks, not the formula.

What this tool IS good for

Understanding the RGB-to-CMYK relationship, filling a CMYK field where an approximation is acceptable, and learning. For actual print work, provide your print shop with the original RGB or HEX value and ask for their color profile. They will convert in software that knows the specific press, paper stock, ink limit and black-generation strategy—none of which this arithmetic can capture. See RGB to HEX Converter for screen color work.