Color to CMYK

What is CMYK?

CMYK is a subtractive color model used in color printing. The four letters stand for Cyan, Magenta, Yellow and Key (black). Unlike the additive RGB model that mixes light to create color on screens, CMYK works by laying down ink on paper — each ink absorbs (subtracts) certain wavelengths of light, and the combination of the four inks reproduces a wide range of colors on white paper.

Each CMYK channel is expressed as a percentage from 0% to 100%, representing how much of that ink is applied. A pure cyan is cmyk(100%, 0%, 0%, 0%), while a rich black is cmyk(0%, 0%, 0%, 100%). Because pure C+M+Y produces a muddy brown rather than a true black, a separate black (Key) plate is added to deepen shadows and reduce ink usage.

How RGB is converted to CMYK

Conversion starts by normalizing RGB to the 0–1 range, then computing the theoretical ink coverage and removing the common "gray component" to avoid over-inking. The standard formula is:

C' = 1 − R/255, M' = 1 − G/255, Y' = 1 − B/255
K = min(C', M', Y')

If K = 1 the color is black and C, M, Y are set to 0. Otherwise each channel is normalized: C = (C' − K) / (1 − K) and likewise for M and Y. The results are multiplied by 100 to give percentages. This tool performs that math live as you pick a color.

When to use CMYK

CMYK is essential whenever color will be physically printed rather than displayed on a screen:

• Print design. Brochures, business cards, packaging and magazines are all produced with CMYK inks.
• Brand guidelines. Print-ready brand specs list CMYK alongside HEX/RGB so logos look consistent on paper.
• Proofing. Converting a screen color to CMYK early helps spot colors that fall outside the printable gamut.
• Signage and large-format printing. Banners and posters use CMYK (sometimes with extra spot colors).

For anything that stays on a screen — websites, app UIs, presentations — keep using RGB or HEX, because CMYK cannot represent the bright saturated colors a monitor can display.

CMYK vs RGB and HEX

RGB and HEX are additive: they describe how much red, green and blue light a screen emits, and can represent very vivid colors. CMYK is subtractive: it describes how much ink is applied to paper, and has a smaller gamut — bright neon greens, deep blues and saturated reds often print duller than they appear on screen. Converting from RGB to CMYK is therefore a one-way gamut compression: some colors shift noticeably.

HEX is the most compact way to share an RGB color digitally; CMYK percentages are the most practical way to specify a print color. Always proof on the actual paper and printer you will use, because the same CMYK values look different on coated, uncoated and newsprint stock.

How to convert a color to CMYK

Converting a color to CMYK with this tool takes a second and runs entirely in your browser. No upload, no sign-up, no install. Follow these steps:

1. Pick a color. Use the color picker, or type red, green and blue values (0–255) into the RGB inputs.
2. Read the result. The Cyan, Magenta, Yellow and Key percentages and the full cmyk() string update live.
3. Copy CMYK. Click "Copy CMYK" to copy the percentage string, then paste it into your design software or print spec.

Every step runs locally in JavaScript, so your color choice never leaves your browser. This makes the tool completely private and instant.