Converter
RGB to CMYK Converter
Enter red, green and blue channel values and get the four process ink percentages. Below the tool: how the maths works, and the more useful question of whether you should be converting at all.
These values are mathematical approximations. Ink, paper, press calibration and colour profile all change the printed result — always approve colour from a physical proof. Full disclaimer.
How the conversion works #
RGB is additive — you start with black and add light. CMYK is subtractive — you start with white paper and take light away. The conversion is essentially an inversion, with one adjustment for the black ink.
Why the same input gives different answers in different apps #
Put 30, 144, 255 into three different tools and you may get three different CMYK results. That is expected, and here is the reason.
The formula above is naive: it knows nothing about ink, paper or press. It is fast, predictable, and produces the numbers most online converters show. Design software does something else. It reads the source profile attached to your file, reads the destination CMYK profile, and maps between them using measured data about how those specific inks behave on that specific stock. That process also applies a rendering intent, which decides what to do with colours that cannot be reached at all.
The profile-aware answer is better whenever you know the press. The naive answer is better when you just need to describe a colour to someone. Neither is wrong.
If a printer has given you a profile name — anything that looks like a coated or uncoated press standard — use it in your design software rather than these numbers. If nobody has given you anything, these numbers are a perfectly reasonable specification to hand over, and the printer will adjust.
Common RGB to CMYK values #
| Colour | RGB | CMYK | Ink |
|---|---|---|---|
| Black | 0, 0, 0 | 0, 0, 0, 100 | 100% |
| White | 255, 255, 255 | 0, 0, 0, 0 | 0% |
| Red | 255, 0, 0 | 0, 100, 100, 0 | 200% |
| Lime | 0, 255, 0 | 100, 0, 100, 0 | 200% |
| Blue | 0, 0, 255 | 100, 100, 0, 0 | 200% |
| Yellow | 255, 255, 0 | 0, 0, 100, 0 | 100% |
| Cyan | 0, 255, 255 | 100, 0, 0, 0 | 100% |
| Magenta | 255, 0, 255 | 0, 100, 0, 0 | 100% |
| Dodger blue | 30, 144, 255 | 88, 44, 0, 0 | 132% |
| Navy | 0, 0, 128 | 100, 100, 0, 50 | 250% |
| Teal | 0, 128, 128 | 100, 0, 0, 50 | 150% |
| Forest green | 34, 139, 34 | 76, 0, 76, 45 | 197% |
| Olive | 128, 128, 0 | 0, 0, 100, 50 | 150% |
| Orange | 255, 165, 0 | 0, 35, 100, 0 | 135% |
| Crimson | 220, 20, 60 | 0, 91, 73, 14 | 178% |
| Maroon | 128, 0, 0 | 0, 100, 100, 50 | 250% |
| Purple | 128, 0, 128 | 0, 100, 0, 50 | 150% |
| Hot pink | 255, 105, 180 | 0, 59, 29, 0 | 88% |
| Silver | 192, 192, 192 | 0, 0, 0, 25 | 25% |
| Charcoal | 54, 69, 79 | 32, 13, 0, 69 | 114% |
Click any row to load that colour into the converter.
Reading the ink coverage figure #
The tool adds the four percentages together and shows the total. Two things this catches:
- Coverage that is too high. Deep colours built from all four inks can exceed what a press can lay down wet. The sheet will not dry cleanly and ink can transfer to the back of the next sheet.
- Registration black. A near-black built as 100 across all four inks is a classic file error. It looks right on screen and causes real problems on press.
Questions #
Should I convert to CMYK myself before sending files to the printer?
Ask them first. Many modern printers prefer to receive RGB and run the conversion themselves through the profile for their press, because they can do it more accurately than you can guess. Others want CMYK files only. Converting when they did not want you to can lose you colour range that was recoverable.
Why does my bright green look dull after converting?
Because it was outside the CMYK gamut. Screens can display saturated greens, oranges and blues that four process inks simply cannot mix. The conversion picks the nearest reachable colour, which is duller. Nothing has gone wrong; you have hit the edge of what printing can do.
Is there a difference between converting RGB to CMYK and hex to CMYK?
No. A hex code is just RGB written in base 16. The conversion is identical once the hex string has been read as three numbers.
Which RGB should I assume, sRGB or Adobe RGB?
The plain formula on this page assumes nothing, which is both its simplicity and its limitation. If your file is tagged Adobe RGB and you convert it with software that respects that tag, you will get different and better numbers, particularly in saturated greens and cyans.
What is the safest workflow for print?
Work in RGB while designing, keep your originals in RGB, convert a copy to CMYK at the end using the profile your printer specifies, then soft-proof and check anything that looked vivid on screen. Never convert back and forth repeatedly; each pass discards information permanently.