ColorKitFree RGB to CMYK converter
RGB to CMYK with the press caveats attached
Paste a hex code or drag the three channel sliders and this free converter returns the four plate percentages, no signup and no upload. Alongside them it reports the total area coverage against the 240% and 300% ink limits, and compares the chroma of your color to what a coated four-color build reaches at that hue — because roughly a third of sRGB is outside CMYK entirely and a converter that hides this hands you a number you cannot print.
- 100% free
- No signup
- Ink coverage total
- Gamut warning
- Rich-black build
#007aff
rgb(0, 122, 255)
Press Ctrl+V anywhere on the page to drop in the hex code from a brand guide — no need to click the field first.
100
Cyan
52
Magenta
0
Yellow
0
Key (black)
cmyk(100%, 52%, 0%, 0%)- Total area coverage
- 152%Inside the 240% ceiling uncoated stock and newsprint run at
- Rounding loss
- ΔE 0.32What whole-percent plates cost you. The arithmetic itself is reversible
Outside a coated process gamut
On screen · C* 77
Chroma ceiling at this hue · C* 59
Ink runs out 18 chroma points short at hue 287°, a gap of ΔE 17.9. The press will land nearer the right-hand swatch than the left.
How to convert RGB to CMYK
Three steps to a separation you can defend in front of a printer.
Put the screen color in
Type or paste the hex code from the brand guide, drag the three channel sliders, or open the system picker next to the field. Anything the site can read is accepted here — bare hex without the hash, rgb(0 122 255), a CSS keyword like firebrick — and the swatch under the sliders confirms you got the color you meant before you read anything off the right-hand column.
Read the four plates and the coverage figure
Cyan, magenta, yellow and key appear as whole percentages, in the order a print brief lists them, with the cmyk() string and a bare C M Y K form for pasting into a spec. Underneath sits the total area coverage — the four numbers added together — which is the figure a printer will query long before they query your hue.
Check the gamut panel before you promise the color
Two swatches sit side by side: your sRGB value and the most chromatic version of that hue a coated four-color build tends to manage. When the panel turns orange the gap is real and it tells you how many chroma points and how much ΔE you are asking the ink to cover. That is the moment to change the color, not after the proof arrives.
Technical specifications
| Conversion | Device-independent sRGB to CMYK: K = 1 − max(R,G,B), the chromatic plates divided by (1 − K). No ICC profile, no under-color removal, no ink-limit clamp |
|---|---|
| Accepted input | Hex in 3, 4, 6 and 8 digits with or without the hash, rgb() and rgba(), hsl() and hsla(), CSS Color 4 slash-alpha, and all 148 CSS color keywords |
| Plate precision | Whole percentages, which is the granularity a press brief and a plate-setter both work in; the rounding cost is displayed as a ΔE and stays under 1.0 across sRGB |
| Coverage ceiling | 300% is the arithmetic maximum of this formula. Practical limits quoted on the page: 240% newsprint and uncoated, 300% sheetfed coated, 300-330% web offset coated |
| Gamut check | Chroma in CIE LCH compared against 12 hue anchors interpolated every 30°, approximating a coated four-color gamut. A heuristic for flagging, not an ICC gamut mapping |
| Rich-black suggestion | Offered when K exceeds 80% with all three chromatic plates under 5%; the build quoted is C60 M40 Y40 K100 at 240% coverage |
| Alpha handling | Dropped. Ink has no alpha channel, so a translucent input is separated as if it were opaque — flatten it against its background first if that matters |
| Cost and processing | Free, no signup, no conversion limit, and the math runs in your tab |
Frequently asked questions
Why do these numbers differ from the ones Photoshop gives me?
Because Photoshop is separating through an ICC profile and this page is not. A profile such as US Web Coated (SWOP), GRACoL 2013 or FOGRA39 carries the measured behavior of a specific press, paper and ink set, plus a black generation strategy that decides how much of a neutral goes into K instead of into equal parts of C, M and Y. The device-independent formula used here has none of that, so it will usually agree on hue and disagree on the split between K and the chromatic plates.
What is total area coverage and why does 300% matter?
Total area coverage is the sum of the four plate percentages, and it is a wetness budget rather than a color property. Sheetfed coated work is generally limited to about 300%, web offset on coated to 300-330%, and newsprint to 240% or less, because past that the sheet stops absorbing ink fast enough and you get set-off, slow drying and mottling. The formula on this page cannot exceed 300% by construction — it pushes every bit of shared ink into K — so a real separation with under-color addition can ask for more than anything you will see here.
How do I know whether my color can be printed at all?
Compare its chroma to the ceiling the gamut panel shows for that hue: roughly a third of sRGB sits outside what four process inks can reach, and the losses are not spread evenly. Screen blue, screen green and the neon oranges fall furthest short, while pale tints, warm reds and most skin tones convert almost invisibly. If the color is a brand asset that must survive the trip, the answer is usually a fifth plate rather than a better formula — see the Pantone reference below for what a spot ink buys you.
Why does my black photograph as dark grey when I print it?
Because a single black plate lays down one ink film and stops at roughly L* 30 on coated stock, which reads as charcoal beside the black your monitor emits. Large solid areas want a rich black — C60 M40 Y40 K100 is the common build at 240% coverage — while small text stays K-only, since four plates on 9pt type shows every fraction of a millimetre of misregistration as a colored fringe.
Should I convert to CMYK myself or hand over RGB files?
Most commercial printers now prefer that you hand over tagged RGB and let their RIP separate with the profile for the press the job is actually running on. Converting early locks in a black generation you cannot undo and throws away gamut you might have kept; converting twice is worse still. Use the numbers here to brief, to sanity-check a proof and to argue about a logo color — not as the file you upload.
Does the ΔE rounding figure tell me how accurate the conversion is?
No — it measures only one small thing, the cost of rounding four plates to whole percentages, and it is normally under 1.0. It is on the page precisely to show where the error is not: the arithmetic reverses cleanly, so the difference you see on a printed sheet comes from the gamut, the profile, the paper and dot gain, none of which a formula can see.
Is the color I type stored anywhere?
No, nothing leaves the tab — the separation, the coverage total and the gamut comparison are all computed by JavaScript already loaded in your browser. There is no upload step and no request per conversion, which is why the sliders keep responding on a plane.
About separating a screen color into ink
RGB and CMYK are not two spellings of one color. RGB is additive and emissive: a monitor starts black and adds light, so its most saturated colors are the ones it can shout loudest. CMYK is subtractive and reflective: paper starts white and every ink film takes something away, so saturation costs coverage and the brightest thing on the sheet is the paper itself. That difference is why the conversion is lossy in one direction and why the interesting question is never “what are the four numbers” but “how much of the color survives”. The plate percentages on this page answer the first question exactly and are honest about the second.
What the arithmetic cannot know is the press. ISO 12647-2 specifies the colorimetry of the process inks, but the sheet that comes off the machine also depends on the stock, the screening, the ink limit and tone value increase — dot gain — which on uncoated paper routinely adds 20% or more to a midtone dot and drags the whole image darker. A profile such as GRACoL 2013 or FOGRA39 encodes all of that from measurements; the formula here encodes none of it. Its one genuine virtue is that it reverses exactly, which the CMYK to RGB page uses to show a whole family of ink builds landing on one screen pixel. Treat both as arithmetic that briefs a conversation, not as a proof.
When a color has to survive the trip rather than merely approximate it, the fix is usually a fifth plate. A spot ink is mixed to a recipe before it ever reaches the press, so it does not care about the process gamut at all — which is the whole reason the Pantone reference exists and why brand guides pin their primary color to one. If the job is staying on screen and you only came here to check a value, the RGB to HEX converter and the hex code chart are the faster route, and neither of them has to apologise for a gamut.
Where the separation is computed
Every number on this page is worked out by JavaScript running in the tab you are reading it in. Nothing you type, paste or open is uploaded, logged or kept, which is also why the tools carry on working after you disconnect from the network.