CMYK to HEX Converter

Screens mix red, green and blue light; printers lay cyan, magenta, yellow and black ink on paper. Designers move between the two constantly: a brand guide lists a colour in CMYK for print and a hex code for the website, or a client sends a colour as percentages and asks what to put in the stylesheet. This converter does the arithmetic in both directions and flags the print problems that show up in the numbers themselves.

The formula

The page uses the standard mathematical conversion. Each of the cyan, magenta, yellow and black values is a fraction between 0 and 1, and each screen channel is the full value of 255 reduced by the ink that absorbs it: red is 255 × (1 − C) × (1 − K), green uses magenta, and blue uses yellow. Going back, black is found as one minus the largest of the three channels, and the other three inks are what is left after removing black. The result is exact algebra, and this is what many web tools and basic design programs do.

A worked example

Press Sample for cyan 0%, magenta 60%, yellow 100% and black 0%. Red stays at full strength because no cyan absorbs it. Green becomes 255 × (1 − 0.6) which is 102, hex 66, and blue becomes 0. The result is #ff6600, the orange shown in the preview, and the RGB readout is 255, 102, 0. The total ink is 160%, within normal limits. Switch to HEX to CMYK and enter #ff6600: the page returns the same 0%, 60%, 100%, 0%, so this particular value round-trips cleanly. Black #000000 becomes 0, 0, 0 and 100% black, and #00ff00 becomes 100% cyan, 0% magenta, 100% yellow.

Total ink and rich black

Add the four percentages for the total ink. Presses can only put down so much ink on a sheet before it fails to dry or smears, so printers set a limit, and many for coated paper work around 300%. A value of 100, 100, 100, 100 totals 400% and triggers a warning. The page also recognises rich black, a black built with other inks for depth, and reminds you that it suits large areas and not small text, where slight misregistration makes the edges colour-fringed. Ask your printer for its actual limit.

Why print will not match

A screen can show colours outside what any ink set can print. The bright #00ff00, which is simply full green light, becomes 100% cyan and 100% yellow in the simple formula, and a real press will reproduce it as a duller green. Paper adds its own effect: uncoated stock absorbs ink and mutes colour. This is why the numbers here are right for the arithmetic but cannot promise how the result will look on paper. Use the printer’s ICC profile in a design program for production files.

Edge cases

Equal CMYK values are not a neutral grey: 50% of all four inks gives a dark, muddy result, and a neutral grey in print is usually black ink alone. The same hex may map to different CMYK values in different programs, because they use different profiles and rendering intents. Going from hex to CMYK the page shows one decimal place, so a colour that is not a clean ink mix reads like 94.9% instead of a round number, and converting back and forth can drift by a fraction.

Limits

No spot colours, Pantone matching or profile conversion is included, and out-of-gamut warnings are not computed, only ink totals. The screen colour you see in the preview is the simple RGB result, not a soft proof of the print. Everything runs in your browser.

Related tools

• Color Converter converts among hex, RGB, HSL and OKLCH.
• Print Bleed Calculator sizes the file for printing.
• Brand Color Palette PDF puts your colours into a one-page brand sheet.
• Color Mixer blends two colours or builds tints and shades.