RGB to CMYK Converter
Convert between RGB, HEX and mathematical CMYK, with a live preview and copyable values.
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How to Use the RGB to CMYK Converter
Choose RGB / HEX or CMYK input mode. Enter whole RGB channels from 0 to 255, or a three- or six-digit HEX code. In CMYK mode enter percentages from 0 to 100. Results update as you edit. Copy RGB, HEX or CMYK separately; Reset restores the example color.
Formula and Explanation
r = R / 255; g = G / 255; b = B / 255 K = 1 − max(r, g, b) If K = 1: C = M = Y = 0 Otherwise C = (1 − r − K) / (1 − K); similarly for M and Y Reverse: R = round(255 × (1 − C) × (1 − K)); similarly for G and B
CMYK inputs and outputs are percentages; the formulas use fractions between 0 and 1. Black has K = 100% and C = M = Y = 0%, avoiding division by zero. Reverse conversion rounds RGB to integer channels. A round trip can choose a different CMYK mixture representing the same mathematical RGB color.
This is an approximate mathematical conversion, not an ICC color-management engine. Paper, inks, press conditions and color profiles change printed appearance. For professional printing use the printer’s requested ICC profile and proofing workflow. The screen preview shows RGB and cannot guarantee a printed match.
Worked Example
RGB (255, 0, 0), HEX #FF0000, gives C = 0%, M = 100%, Y = 100%, K = 0%. RGB black (0, 0, 0) gives only K = 100%. For RGB (128, 128, 128), K is approximately 49.8039% and C, M and Y are zero.
Frequently Asked Questions
Why can the printed color look different?
Screens emit light, while inks reflect light from paper. Printer gamut, ink and paper affect the result; the simple formula does not account for them.
Does this converter use ICC profiles?
No. It uses the displayed mathematical formula. Use color-managed design software with the correct printer profile for press-specific output.
Can I enter a short HEX code?
Yes. Three-digit codes expand each digit: #F80 becomes #FF8800. Six-digit codes are also accepted, with or without the leading #.
Why can CMYK values change after a round trip?
Different CMYK mixtures can produce the same mathematical RGB color. RGB rounding and the formula’s black extraction can change the returned mixture.
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