RGB to CMYK Converter

Convert an RGB color to CMYK — or CMYK back to RGB — with a live swatch preview. Useful for a quick estimate when moving a color from screen design toward print.

CMYK formula

Formula (RGB values 0–255, results as percentages)

K = 1 − max(R′, G′, B′), where R′ = R÷255, etc. C = (1 − R′ − K) ÷ (1 − K) M = (1 − G′ − K) ÷ (1 − K) Y = (1 − B′ − K) ÷ (1 − K) Example: RGB(37, 99, 235) → CMYK(84%, 58%, 0%, 8%)

Why this is an estimate, not a print-accurate conversion

There's no single, universally correct way to turn RGB into CMYK. A real printing press's actual CMYK output depends on the specific ink set, paper stock, and press calibration — professional print workflows use a color profile (ICC profiles like SWOP, FOGRA, or GRACoL) calibrated to the exact printer being used. This calculator uses the standard simplified, device-independent formula that every online CMYK converter is built on. It's a useful, consistent estimate for screen mockups or a rough sense of the values — it isn't a substitute for proofing through your actual print software before sending a job to a commercial printer.

There's also a small, unavoidable rounding effect worth knowing about: CMYK is conventionally shown as whole-number percentages (0–100), which holds less precision than 8-bit RGB (0–255). Converting RGB to CMYK and back can shift a channel by a value or two out of 255 — visually invisible, but the reason a perfect round-trip isn't always possible with any CMYK converter, not just this one.

Colors with RGB, HEX, and HSL values

Gold Colors Green Colors Pink Colors Brown Colors Orange Colors Blue Colors Purple Colors Yellow Colors Spring Colors True Summer Color Palette Fall / Autumn Colors Dark Winter Color Palette

Frequently asked questions

What is the CMYK formula?

K (black) is 1 minus the largest of the three RGB values (scaled 0 to 1). C, M, and Y are then each calculated from how far their matching RGB channel is from that maximum, adjusted for how much black is already present.

Is this CMYK value exactly what a printer will produce?

No — treat it as a close estimate, not a guarantee. Real print output depends on the specific ink, paper, and press profile in use, which this calculator has no way to know. For final print production, proof the color through your actual print software's color profile rather than relying on this or any generic online CMYK converter.

What does the K in CMYK stand for?

Key, referring to the key plate that historically carried the black detail in four-color printing — not "black" itself, though it's commonly explained that way since K is the black channel.