RGB to CMYK Converter
Convert any RGB color to CMYK percentages instantly. Enter R, G and B values from 0 to 255 and see Cyan, Magenta, Yellow and Key with the formula and a live swatch.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the RGB to CMYK Converter Works
This tool converts a screen color in RGB (red, green, blue from 0 to 255) into the four CMYK ink percentages — Cyan, Magenta, Yellow and Key (black) — used in print. Enter your RGB values and it shows the CMYK result, a color swatch and the matching hex code.
The Formula
First normalise each channel to the 0–1 range, then derive the black channel and the three color channels:
R’ = R ÷ 255, G’ = G ÷ 255, B’ = B ÷ 255 K = 1 − max(R’, G’, B’) C = (1 − R’ − K) ÷ (1 − K) M = (1 − G’ − K) ÷ (1 − K) Y = (1 − B’ − K) ÷ (1 − K)
If the color is pure black (R = G = B = 0), then K = 1 and C, M, Y are all set to 0.
Worked Example
Take the violet RGB (139, 92, 246):
- R’ = 139 ÷ 255 = 0.545, G’ = 92 ÷ 255 = 0.361, B’ = 246 ÷ 255 = 0.965
- K = 1 − max(0.545, 0.361, 0.965) = 1 − 0.965 = 0.035 → 4%
- C = (1 − 0.545 − 0.035) ÷ (1 − 0.035) = 43%
- M = (1 − 0.361 − 0.035) ÷ 0.965 = 63%
- Y = (1 − 0.965 − 0.035) ÷ 0.965 = 0%
So RGB (139, 92, 246) is approximately CMYK 43%, 63%, 0%, 4%.
Why Convert RGB to CMYK?
Designs are created on screen in RGB but printed in CMYK ink. Converting early helps you:
- Preview print color before sending files to a printer
- Spot out-of-gamut colors that will look duller on paper
- Build print-ready files with the correct color values
Screen vs. Print
| Color | RGB | CMYK |
|---|---|---|
| Black | 0, 0, 0 | 0%, 0%, 0%, 100% |
| White | 255, 255, 255 | 0%, 0%, 0%, 0% |
| Red | 255, 0, 0 | 0%, 100%, 100%, 0% |
| Violet | 139, 92, 246 | 43%, 63%, 0%, 4% |
Frequently asked questions
How do I convert RGB to CMYK?+
Divide each RGB value by 255 to get R', G' and B'. Find K = 1 − max(R', G', B'). Then C = (1 − R' − K) / (1 − K), M = (1 − G' − K) / (1 − K) and Y = (1 − B' − K) / (1 − K). Multiply each result by 100 for percentages.
What is the CMYK of black in RGB?+
Pure black is RGB (0, 0, 0). The formula gives K = 1 − max(0,0,0) = 1, so CMYK is 0%, 0%, 0%, 100%. In print this is often replaced with a 'rich black' that adds some cyan, magenta and yellow.
Why do RGB and CMYK colors look different?+
RGB is an additive model for screens that emit light, while CMYK is subtractive and made for ink on paper. CMYK has a smaller gamut, so bright, saturated RGB colors often appear duller once printed. Always proof on the target device.
Is this RGB to CMYK conversion exact for printing?+
The math here is the standard device-independent formula, which is great for estimating values. True print color also depends on the printer, inks, paper and ICC profile, so a calibrated profile is needed for color-critical print work.
What does the K in CMYK stand for?+
K stands for Key, the key plate that carries the black ink and the finest detail. Black is printed separately rather than mixing C, M and Y because that saves ink and produces a deeper, cleaner black.