How to Use This Tool
Enter a colour. You get the CMYK values, an estimate of how far outside print's reach the colour sits, and a preview of what ink can actually achieve.
Why this conversion is approximate by nature
RGB describes light and CMYK describes ink on paper. The translation depends entirely on which ink and which paper: the same four numbers produce a noticeably different colour on uncoated newsprint than on glossy coated stock, because the paper absorbs ink differently and reflects differently.
A proper conversion uses an ICC profile that describes a specific press, ink set and substrate. Common ones are US Web Coated for American commercial printing and Coated FOGRA for European. A browser has no access to those, so what any online converter gives you — including this one — is the naive arithmetic conversion. It is a reasonable starting point and it is not what will come off the press.
What the gamut warning means
Some colours simply cannot be made with ink. Saturated greens, vivid oranges, bright cyans and anything that looks like it is glowing are outside the CMYK gamut entirely. The conversion still returns four numbers, because the arithmetic always produces something — but the result is the nearest printable colour, and the difference is quietly discarded.
That is why the two swatches above are shown side by side. If they look different, the colour you picked cannot be printed and you are seeing what you will actually get. This is the single most common surprise in print work: a brand colour that looks electric on screen arrives dull and nobody warned anyone.
Total ink coverage
The four percentages added together is the total ink coverage, and presses have a limit — commonly 240% for newsprint, up to about 300% for coated stock. Exceed it and the ink cannot dry properly, which causes offsetting onto the next sheet, smearing, and paper cockling.
The naive conversion never checks this, so it can produce values a printer will reject. The panel above shows the total so you can see it before the print shop does.
Practical advice
- Do not convert RGB to CMYK yourself if you can avoid it. Send RGB files and let the print shop convert with the profile for their press. They know their equipment and you do not.
- For brand colours that must match, specify a spot colour such as a Pantone, which is a pre-mixed ink rather than a four-plate approximation. It costs more and it is the only way to be certain.
- Check the proof, not the screen. A printed proof on the actual stock is the only reliable preview, and it is cheap next to reprinting a run.
- Small black text should be 0/0/0/100. Any other mix requires four plates to line up perfectly, and slight misregistration on small type is very visible.
