CMYK ↔ RGB Converter

How to use CMYK ↔ RGB Converter

1. Enter CMYK percentages, or an RGB or hex value.
2. Read the conversion in the other model.
3. For anything going to print, check the result against a physical swatch rather than your screen.
4. CMYK values are ink coverage percentages from 0 to 100.
5. Round-tripping RGB to CMYK and back shifts slightly — the smaller gamut and whole-percent rounding both lose a little.
6. Pure black text should be K only; a rich black mix is for large solid areas.

Two models that work in opposite directions

RGB is additive: screens emit light, and all three channels at full strength give white. CMYK is subtractive: ink absorbs light reflected off paper, and more ink means darker, with no ink at all giving whatever colour the paper is. That is why a screen can show a luminous cyan that no printer reproduces — the screen is emitting light and the page can only fail to absorb it. The K channel exists because mixing C, M and Y to make black produces a muddy brown, wastes ink and soaks the paper.

Why the conversion is an approximation

The formula here is the standard mathematical one, and real print colour depends on the specific ink set, the paper, the press and the ICC profile that ties them together. The same CMYK values print noticeably differently on coated and uncoated stock, because uncoated paper absorbs ink and dulls it. Professional workflows convert through a profile such as FOGRA39 or GRACoL, not through arithmetic. Treat this tool as a close estimate for getting into the right region, and proof properly before a print run.

The gamut problem, in the direction that hurts

CMYK’s gamut is smaller than sRGB’s, so a vivid screen colour — bright orange, saturated green, electric blue — has no ink equivalent and comes back noticeably duller. This is the call people get from their printer. If a brand colour matters, choose it from a printed swatch book rather than on screen, and consider a Pantone spot colour, which is premixed ink rather than a halftone of four and reproduces exactly at the cost of an extra plate.

Practical rules for print files

Black text should be 100% K alone, never a four-colour mix: registration on a press is never perfect, and small text built from four plates shows colour fringing. Large solid blacks want a rich black, typically around 60C 40M 40Y 100K, which looks genuinely black rather than washed out. Keep total ink coverage under about 300% or the sheet will not dry properly. And supply files in CMYK if the printer asks for CMYK — letting them convert means they choose, not you.