RGB to CMYK Converter
Turn screen RGB colours into print CMYK values.
How to use
- 1 Type the red, green and blue values (0–255), or pick a colour with the swatch.
- 2 Read the CMYK percentages shown below the inputs.
- 3 Copy the cmyk(…) string into your design tool or print spec.
- 4 Adjust a channel to see the CMYK values update live.
About RGB to CMYK Converter
The RGB to CMYK Converter translates the additive colours your screen uses into the subtractive ink percentages a printer needs.
Monitors build colour by adding red, green and blue light, while printing presses and desktop printers lay down cyan, magenta, yellow and key (black) ink on white paper.
Whenever you move a design from screen to print you have to bridge these two models, and this tool does the arithmetic for you.
Enter each channel as a value from 0 to 255, or use the colour picker to choose a swatch and have the red, green and blue fields fill in automatically.
The converter applies the standard device formula: it first finds the key (black) component from the brightest channel, then derives cyan, magenta and yellow relative to that black.
Pure white returns all zeros, pure black returns 100% key, and everything in between is reported as tidy percentages rounded to two decimals, ready to paste into design software or a print spec.
Keep in mind that this is a mathematical conversion, not a colour-managed one: real presses use ICC profiles to account for paper, ink and dot gain, so treat the numbers as an accurate starting point rather than a guaranteed proof.
Everything runs in your browser with nothing uploaded, so it is fast, private and works offline.
FAQ
Why do my printed colours look different from the screen?
RGB light and CMYK ink cover different gamuts, and presses use ICC profiles for paper and ink. This converter gives a faithful mathematical starting point, not a colour-managed proof.
How is the black (key) channel calculated?
Key is 1 minus the largest of the normalised red, green and blue values. Cyan, magenta and yellow are then derived relative to that key amount.
What does pure black convert to?
Pure black (0, 0, 0) converts to 0% cyan, magenta and yellow with 100% key, because all the colour comes from black ink.