Home › Converters › RGB to CMYK Converter
RGB to CMYK Converter
Use this free RGB to CMYK converter to change any color between the screen model (RGB) and the print model (CMYK). Enter red, green, and blue values from 0 to 255, or cyan, magenta, yellow, and black percentages from 0 to 100, and the converter shows the matching color both ways — with a live color swatch, the hex code, and a color picker to try any shade.
How it works
Screens and printers make color in opposite ways. A screen starts black and adds light: red, green, and blue light mixed together make white, and every color on a monitor is some mix of those three channels, each from 0 to 255. A printer starts with white paper and subtracts light with ink: cyan, magenta, and yellow inks absorb parts of the light, and black ink is added for depth. Because the two systems work in opposite directions, a color has to be translated — and that translation is what this converter does.
Converting RGB to CMYK starts with the black channel, K. Take the brightest of the three RGB values, divide it by 255, and subtract from 1. A bright color has a high maximum, so K is small; a dark color has a low maximum, so K is large. For the blue in the default example, RGB (37, 99, 235), the maximum is 235, so K = 1 − 235 ÷ 255 = 0.0784, or 7.84 percent.
Once K is known, each ink channel follows the same formula: take the channel's share of light, subtract K, and divide by what is left after black. Cyan is (1 − R ÷ 255 − K) ÷ (1 − K), magenta uses the green value, and yellow uses the blue value, each multiplied by 100 to give a percentage. For the default blue, cyan is (1 − 37 ÷ 255 − 0.0784) ÷ 0.9216 = 84.26 percent, magenta is 57.87 percent, and yellow is 0 percent, because the blue channel is already at its maximum. The one special case is pure black, RGB (0, 0, 0): there K is 1, the formula would divide by zero, and the answer is simply C = 0, M = 0, Y = 0, K = 100 percent.
Going the other way, CMYK to RGB, is simpler. Each RGB channel is 255 times what the inks leave behind: R = 255 × (1 − C ÷ 100) × (1 − K ÷ 100), with M for green and Y for blue. So CMYK (0%, 100%, 100%, 0%) gives R = 255 × 1 × 1 = 255, G = 255 × 0 × 1 = 0, B = 255 × 0 × 1 = 0 — pure red, RGB (255, 0, 0). The black channel darkens all three channels equally, which is exactly what black ink does on paper.
The hex code is the same RGB color written in base 16: each channel from 0 to 255 becomes two hex digits, so RGB (37, 99, 235) is #2563EB — 37 is 25 in hex, 99 is 63, and 235 is EB. The live swatch above the result shows the color itself, so you can see at a glance whether the conversion looks right, and the color picker lets you grab any shade from a palette and read off its RGB, CMYK, and hex values in one step.
Two practical warnings belong here. First, the CMYK range of printable colors is smaller than the RGB range a screen can show, so very bright blues, greens, and oranges will print duller than they look on screen — the CMYK numbers are the closest the printer can get, not an exact match. Second, the same CMYK percentages can look slightly different on different printers and papers, because ink, paper, and calibration all shift the result. For anything that has to match exactly, such as a logo, ask the printer for a proof before running the full job.
Worked example
Convert pure red, RGB (255, 0, 0), to CMYK.
Step 1: Find K — the brightest channel is 255, so K = 1 − 255 ÷ 255 = 1 − 1 = 0%.
Step 2: Find cyan — C = (1 − 255 ÷ 255 − 0) ÷ (1 − 0) = 0 ÷ 1 = 0%.
Step 3: Find magenta — M = (1 − 0 ÷ 255 − 0) ÷ (1 − 0) = 1 = 100%.
Step 4: Find yellow — Y = (1 − 0 ÷ 255 − 0) ÷ (1 − 0) = 1 = 100%.
So RGB (255, 0, 0) equals CMYK (0.00%, 100.00%, 100.00%, 0.00%), with hex code #FF0000. Try it in the converter: enter 255, 0, 0 and it shows exactly those percentages, and the swatch turns pure red.
FAQ
What does CMYK stand for?
CMYK stands for cyan, magenta, yellow, and key — key is the black ink. It is the color model used by printers, which build colors by layering ink on paper. RGB, by contrast, is the model used by screens, which build colors by adding red, green, and blue light.
How do I convert RGB to CMYK?
First find K, the black: K = 1 − max(R, G, B) ÷ 255. Then each other channel is (1 − channel ÷ 255 − K) ÷ (1 − K), times 100 for a percentage. If K is 1 — pure black — then cyan, magenta, and yellow are all zero. Enter your RGB values above and the converter does it instantly.
Can every RGB color be printed in CMYK?
No. Screens can show bright, saturated colors — vivid blues, greens, and oranges — that ink on paper cannot reproduce, because CMYK has a smaller color range, called a gamut. When you convert a very bright RGB color, the CMYK result is the closest printable match, and it usually looks a little duller than it did on screen.
Why is black a separate ink instead of mixing cyan, magenta, and yellow?
Mixing all three inks does make a dark color, but it is a muddy brown-black, and it uses three times as much ink. A dedicated black ink gives a true, crisp black, sharper text, and cheaper printing. That is why the K in CMYK stands for 'key' — the key plate that carries the detail and the black.
How do I convert CMYK back to RGB?
Use R = 255 × (1 − C ÷ 100) × (1 − K ÷ 100), and the same formula for green with M and blue with Y. For example, CMYK (0%, 100%, 100%, 0%) gives RGB (255, 0, 0) — pure red. Switch the direction above to CMYK to RGB and the converter does it for you.