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Page Utils

RGB to CMYK

RGB to CMYK conversion turns screen colours (red, green, blue, 0–255) into print ink percentages (cyan, magenta, yellow, key/black, 0–100%): K = 1 − max(R′,G′,B′), then each ink = (1 − channel − K) / (1 − K). This browser page does it live, reverses CMYK to RGB, uploads nothing, and is not an ICC or Pantone match.

Updated

Convert RGB to CMYK entirely in this browser tab — or flip to CMYK → RGB when you already have print percentages. Enter R/G/B from 0 to 255 (or C/M/Y/K from 0 to 100), read the matching channels, hex, and a colour swatch, then copy the string you need. Closing the tab clears the workspace; nothing is uploaded or written to localStorage.

The math is the common device-independent undercolour-removal formula (K = 1 − max(R′,G′,B′), then C/M/Y from the remainder). It is not an ICC press profile, not a Pantone lookup, and not a claim that your printer will match the swatch. Soft-proof in the design app that owns your colour management when you need press accuracy.

RGB ↔ CMYK workspace

RGB → CMYK

Each channel is an integer from 0 to 255. Conversion is local — nothing is uploaded.

Enter RGB 0–255 (or CMYK 0–100%) and convert locally. Load example fills a fictional orange sample. Closing the tab clears the workspace.

This converter uses the common undercolour-removal formula in your browser. It is not a print-shop ICC profile, does not upload colours, and does not write localStorage. For press work, soft-proof in the application that owns your colour profile.

How does the RGB to CMYK work?

  1. 1. Enter RGB (or CMYK)

    Type R, G, and B from 0 to 255 — or switch to CMYK → RGB and enter C/M/Y/K percentages. Load example fills a fictional orange sample.

  2. 2. Convert locally

    The tab runs the classic undercolour-removal formula. Nothing is uploaded and no ICC profile is fetched.

  3. 3. Read swatch and strings

    See a live swatch plus rgb(), hex, and cmyk() percentages. Values stay in React state for this tab only.

  4. 4. Copy the result

    Copy the CMYK or RGB string. Closing the tab drops the workspace. Need CSS or HTML formatting instead? Use CSS Formatter or HTML Formatter on this hub.

Questions about RGB to CMYK

How do I convert RGB to CMYK by hand?
Divide R, G and B by 255, take K = 1 − the largest of the three, then C = (1 − R′ − K) / (1 − K), and M and Y the same way with G′ and B′. Example: RGB(255, 153, 51) gives R′ 1, G′ 0.6, B′ 0.2, so K = 0 and CMYK ≈ 0%, 40%, 80%, 0%. Pure black (K = 1) is CMYK 0, 0, 0, 100.
What does this RGB to CMYK converter do?
It converts RGB channels (0–255) into CMYK percentages with a classic undercolour-removal formula, and can reverse CMYK back to RGB. You get a live swatch plus copyable rgb(), hex, and cmyk() strings. Everything runs in your browser — no signup and no upload.
Does it upload my colour values?
No. Conversion is pure in-page math. There is no account, no server-side colour API, and no file upload. Channel values stay in this tab until you clear them or close the page. We do not write colour channels to localStorage or send them to a remote colour service.
Is this an ICC press profile or Pantone match?
No. The page uses the common device-independent RGB↔CMYK formula for quick drafts. It does not load ICC profiles, soft-proof for a specific press, or look up Pantone libraries. For print production, soft-proof in the application that owns your colour management.
Why is there no /rgb-to-cmyk-converter/ or /convert-rgb-to-cmyk/ second URL?
One canonical address with a trailing slash: /developer/rgb-to-cmyk/. Queries like "rgb to cmyk converter" or "convert rgb to cmyk" can land here. We do not publish stub alias slugs that would split the address people and search engines should share, and we do not leave empty converter URLs that 404.
What formula does RGB → CMYK use?
Normalize each RGB channel to 0–1, set K = 1 − max(R′, G′, B′), then C/M/Y = (1 − channel − K) / (1 − K) when K is not 1 (pure black). Results are shown as percentages from 0 to 100. The reverse multiplies (1 − C)×(1 − K) (and M/Y likewise) back to 0–255 RGB.
How is this different from CSS Formatter on this hub?
CSS Formatter pretty-prints or minifies stylesheet text. RGB to CMYK converts colour channel numbers between RGB and CMYK. They share the same privacy rule (local only) but solve different jobs — this page does not format CSS, and CSS Formatter does not convert colour models.
Can I paste a hex colour like #FF9933?
v1 accepts decimal RGB 0–255 (and CMYK percentages on the reverse path). Hex is shown in the output for convenience after you convert, but there is no dedicated hex paste field yet. Enter R=255, G=153, B=51 (or press Load example) for the fictional orange sample; a hex input may ship later without a second URL.
Is anything stored in localStorage?
No. Channel fields live in React state for this tab only. Closing the tab clears them, and we do not mirror RGB or CMYK values into localStorage or cookies. Hosting logs may show that you requested the page URL, not the colours you typed.

What else can I open?

These tools run in your browser. Page Utils does not store, upload, or write to localStorage the keys, tokens, or text you paste. Results are a convenience aid, not legal, tax, or security advice.