About the RGB to CMYK
Print uses CMYK inks (cyan, magenta, yellow, black) while screens use RGB light, so a conversion is needed when preparing artwork for print. This tool converts RGB, or any colour you enter, to CMYK percentages. Convert several at once, one per line.
The rule it applies is short: K is one minus the largest of the three normalised channels, and each ink is then that channel's shortfall divided by whatever K has left behind. Pure black therefore comes out as 0, 0, 0, 100 rather than as a mix of all four inks. For body text that is exactly right, but for a large solid black panel it is not, because print shops build a rich black with extra cyan underneath to stop it looking grey on the page.
Gamut is the deeper limitation. Ink on paper reflects light while a screen emits it, so the bright saturated greens, oranges and blues a display can reach have no ink equivalent, and a colour such as rgb(31, 193, 107) will always print duller than it looks here. Any colour carrying brand weight should be checked on a physical proof before a run is signed off, not judged from a monitor.
The conversion is a standard mathematical approximation; exact print colour depends on the paper, inks and colour profile, so treat the result as a starting point and confirm with your printer's profile. To convert CMYK back, use CMYK to RGB; to find the nearest spot colour instead of a four-ink build, try RGB to Pantone.
How to use
- Paste RGB or HEX colours, one per line.
- Copy the cmyk() percentages.
- Confirm against your print profile for exact colour.
Common questions
- Is the CMYK exact?
- It is a standard approximation. True print colour depends on the ICC profile, paper and inks, so use it as a starting point.
- Can I enter HEX instead of RGB?
- Yes, any colour format is accepted.
- Why is black (K) separate?
- Print uses a dedicated black ink for depth and to save coloured ink, so CMYK has a K channel.