#rrggbb).CMYK (Cyan, Magenta, Yellow, Key/Black) is the colour model used in professional printing. RGB is the model for screens. Converting between them is necessary when you are designing for both print and digital — a logo that looks vibrant on screen may print duller if the CMYK conversion is not handled carefully.
RGB is an additive model: mixing red, green, and blue light creates white. CMYK is a subtractive model: inks absorb light, and mixing all three absorbs most wavelengths — ideally producing black (but in practice, a muddy brown, hence the separate Key/Black ink). The RGB colour space is larger than the printable CMYK gamut, so vivid digital colours (especially bright blues and oranges) cannot be reproduced exactly in print. Professional workflows use ICC profiles and soft-proofing to preview this gap.
The mathematical conversion from RGB to CMYK is not a perfect round-trip. Floating-point rounding and the different colour spaces mean you often get values off by 1–2 units. For production print work, use ICC profiles in Photoshop or Illustrator rather than mathematical conversion.
K stands for Key, meaning the Key colour — black. "Key" refers to the key plate in printing that carries the detail and sharpness of the image. Using black ink separately gives cleaner blacks than mixing CMY.
Yes, but remember that the conversion is approximate. Very saturated or vivid RGB colours may fall outside the CMYK printable gamut. Always review the CMYK values with your print provider before finalising.
Colours that exist in RGB but cannot be reproduced in CMYK are called out-of-gamut. They are typically very bright, highly saturated colours. Print software will substitute the nearest printable colour, which may look noticeably different.
See also the Colour Name Finder, HEX Color Picker, and HSL to RGB converter.
CMYK is the standard colour model for print design. Converting RGB or hex web colours to CMYK before sending artwork to print avoids colour surprises — screens use additive light mixing while printers use subtractive ink mixing, so the same value produces different results. Always verify a physical proof before committing to a large print run. This converter handles the standard CMYK formula and is accurate for most commercial printing workflows.