HEX to CMYK converter
Convert a screen hex colour into approximate CMYK ink percentages for print, with a clear statement of what that approximation can and cannot promise.
- Runs in your browser
- Nothing you enter is sent
- Free, no account
Three, four, six or eight hex digits, with or without the leading #.
Converted from HEX.
Contrast on white
5.17:1
AA for body text
Contrast on black
4.06:1
AA for large text only
| Format | Value | Copy |
|---|---|---|
| HEX | #2563eb | |
| HEX with alpha | #2563ebff | |
| RGB | rgb(37, 99, 235) | |
| RGBA | rgba(37, 99, 235, 1) | |
| RGB (space syntax) | rgb(37 99 235) | |
| HSL | hsl(221.2, 83.2%, 53.3%) | |
| HSLA | hsla(221.2, 83.2%, 53.3%, 1) | |
| HSL (space syntax) | hsl(221.2 83.2% 53.3%) | |
| HSV / HSB | hsv(221.2, 84.3%, 92.2%) | |
| CMYK | cmyk(84.3%, 57.9%, 0%, 7.8%) | |
| Android ARGB | #FF2563EB | |
| SwiftUI | Color(red: 0.145, green: 0.388, blue: 0.922) | |
| Nearest CSS name | royalblue (closest match) |
CSS custom properties
--color: #2563eb; --color-rgb: 37 99 235; --color-hsl: 221.2 83.2% 53.3%;
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Why this matters
In 2025 researchers found that popular online formatters had retained tens of thousands of user-submitted snippets — JSONFormatter.org and CodeBeautify together exposed roughly 80,000 saved documents, many containing live cloud credentials, private keys and internal database connection strings, because “format this” quietly meant “upload this”. A separate incident exposed roughly 3.5 million user PDFs on a document-conversion service. The only structural fix is not sending the data in the first place: this site is served under a Content-Security-Policy whose connect-src contains no third-party origin, so a request off this device cannot be made even by accident.
The formula, and its honest limits
This is the naive, device-independent conversion — the same arithmetic design software uses when colour management is switched off.
#2563eb → r=0.145 g=0.388 b=0.922 (normalised)
K = 1 - max(r, g, b) = 1 - 0.922 = 0.078 → 7.8%
C = (1 - r - K) / (1 - K) = 0.844 → 84.4%
M = (1 - g - K) / (1 - K) = 0.577 → 57.7%
Y = (1 - b - K) / (1 - K) = 0.000 → 0%
cmyk(84.4%, 57.7%, 0%, 7.8%)Note what the formula does not know: the paper, the ink set, the press, the dot gain, or the colour profile. A real conversion is a lookup through an ICC profile that encodes all of those. Treat these numbers as a starting point and a way to communicate approximately — not as artwork values.
Why K exists
In theory, 100% cyan plus 100% magenta plus 100% yellow absorbs all light and produces black. In practice it produces a muddy dark brown, uses three times the ink, soaks the paper enough to cockle it, and takes far longer to dry. So black is printed directly with its own plate — the K in CMYK, for “key” — and subtracted from the other three. That subtraction is why the formula computes K first.
A practical consequence: never specify black text as cmyk(0, 0, 0, 100)’s
opposite. Body text should be 100% K only. Four-colour black on small text produces visible
registration fringes if the plates are a fraction of a millimetre out.
Out-of-gamut colours
sRGB and CMYK cover different regions of visible colour, and sRGB’s includes bright saturated cyans, greens, oranges and pure blues that no ink combination can reproduce. Those colours are “out of gamut”: the conversion returns the closest printable colour, which is duller and often shifted in hue.
| Screen colour | What happens in print |
|---|---|
Vivid RGB blue #0000ff | Comes out noticeably purple |
Bright green #00ff00 | Loses most of its intensity |
| Neon orange, hot pink | Flattens considerably |
| Anything fluorescent | Needs a spot ink; CMYK cannot do it at all |
Nothing in the arithmetic can fix this. It is a physical limit of subtractive ink on reflective paper versus additive light on a display.
Total ink coverage
Add the four percentages together and you get total area coverage. Most commercial presses cap it at 240–320% depending on paper stock; exceed it and the sheet stops drying properly and offsets onto the next one. If your converted values sum above 300%, ask the printer before proceeding — a rich black is usually specified as something like 60/40/40/100, which is 240%, rather than 100/100/100/100.
What to actually send to a printer
Ask them first — the answer varies. Most commercial printers today prefer a PDF/X file with a declared output intent and will run the conversion themselves using the correct profile, which gives a better result than a conversion you did with no profile at all. Use these numbers to set expectations, to match a brand colour approximately, and to fill in a field on a form that demands CMYK. For brand colours that must be exact across media, the answer is a spot colour (Pantone), not a CMYK approximation.
Questions
How accurate is this conversion?
It is the naive, device-independent formula — the same one design software uses when colour management is switched off. It is a reasonable starting point and it is not a press-ready separation. A real conversion depends on an ICC profile for the specific paper, ink and press.
Why does my bright screen colour look dull in print?
Because sRGB can display colours that CMYK ink cannot reproduce — saturated cyans, greens and oranges especially. Those are "out of gamut": the conversion picks the closest printable colour, which is duller. Nothing in the maths can fix that; it is a physical limit of ink on paper.
What is the K channel for?
Black. In theory equal amounts of cyan, magenta and yellow make black; in practice they make a muddy brown, soak the paper and cost three times as much ink. K prints black directly and is subtracted from the other three, which is why the formula computes it first.
What should I give my printer?
Ask them. Most commercial printers want a PDF with a specific output intent, or they will run the conversion themselves from your RGB file using the right profile. Use these numbers to set expectations and to match a brand colour approximately, not as final artwork values.