Result
This page has no server side at all. The table you paste is parsed by JavaScript inside your own browser, the chart is drawn on a canvas element on your machine, and the export file is assembled locally. Nothing is uploaded, stored or written to any log. You can disconnect from the network after the page has loaded and everything will still work — which is the simplest way to verify the claim yourself.
Facts and limits of this method
| Black formula | K = 1 − max(R, G, B) / 255 |
|---|---|
| Cyan formula | C = (1 − R/255 − K) / (1 − K) |
| Input range | R, G, B from 0 to 255 |
| Output range | C, M, Y, K from 0% to 100% |
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.
- RGB is an additive model for screens, CMYK is subtractive for ink on paper; some saturated RGB colors (especially bright blues and greens) 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 (Adobe, CorelDRAW, etc.) before printing a run.
How it is calculated
R, G and 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 — the darker the source color, the higher K is.
Each of cyan, magenta and yellow is computed as (1 − channel − K) / (1 − K), which removes the black contribution from the color components.
The resulting C, M, Y and K fractions are multiplied by 100 and rounded to give print-ready percentages.
Questions and answers
Why does CMYK look different on screen than on paper?
A screen displays light (RGB), while paper shows reflected light after ink is applied (CMYK), so the final printed shade should always be checked with a proof.
Can I use these percentages directly in a print layout?
As a guideline, yes, but before printing a run it's worth confirming exact values against the specific print shop's color profile.
Why doesn't C + M + Y + K add up to 100%?
That's normal: each CMYK channel is an independent ink-coverage percentage, not a share of a 100% total.
Is my data sent anywhere?
No, the whole calculation runs in your browser.