Result
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Facts and limits of this method
| Supported formats | 3-digit (#RGB) and 6-digit (#RRGGBB) HEX |
|---|---|
| Intermediate step | HEX is first converted to RGB, then to CMYK |
| Output range | C, M, Y, K from 0% to 100% |
| Letter case | Uppercase and lowercase A–F are equivalent |
When it misleads you
- This is a mathematical approximation, not real color separation — actual print shops use ICC profiles for a specific printer and paper, which produce different numbers.
- HEX and RGB are screen models, CMYK is for ink on paper; some saturated screen colors can't physically be reproduced in CMYK and will print duller.
- The formula assumes the simplest black generation (100% GCR), while professional prepress uses more sophisticated ink-mixing schemes.
- Treat the result as a design-time guideline, not final press values — verify them in dedicated software before printing a run.
How it is calculated
The HEX code is parsed into three channels — red, green and blue, each from 0 to 255 (a shorthand 3-digit code is first expanded to 6 digits).
R, G, B values are normalized by dividing by 255, giving numbers from 0 to 1.
The black channel K is computed as one minus the maximum of the normalized R, G, B.
Each of cyan, magenta and yellow is computed as (1 − channel − K) / (1 − K), and the result is multiplied by 100 to give CMYK percentages.
Questions and answers
Why does the color look different on screen than printed?
A screen shows light (RGB/HEX), while paper shows reflected light after ink is applied (CMYK), so the final printed shade should always be checked with a proof.
Can I enter HEX without the # symbol?
Yes, the # is optional — the converter understands the code with or without it.
Does shorthand 3-digit HEX work?
Yes, the converter automatically expands it to the full 6-digit form before calculating.
Is my data sent anywhere?
No, the whole calculation runs in your browser.