CMYK to RGB Converter

CMYK describes the four printing inks — cyan, magenta, yellow and key (black) — while RGB describes the red, green and blue light a screen emits. This converter turns CMYK ink percentages into the equivalent RGB value with a live colour swatch, so you can preview a print colour on screen or pull a print value into web and CSS work.

How it works

The tool applies the standard mathematical CMYK-to-RGB conversion (used when no ICC colour profile is involved). Each ink percentage is divided by 100, then each RGB channel is computed as 255 scaled down by the relevant ink and by black:

R = 255 × (1 − C) × (1 − K) G = 255 × (1 − M) × (1 − K) B = 255 × (1 − Y) × (1 − K)

Higher ink values subtract more light, and the black (K) channel dims all three at once. Results are rounded to whole 0-255 values and shown as a CSS rgb() string.

Worked example

Convert C 76, M 47, Y 0, K 4:

• R = 255 × (1 − 0.76) × (1 − 0.04) = 255 × 0.24 × 0.96 ≈ 59
• G = 255 × (1 − 0.47) × (1 − 0.04) = 255 × 0.53 × 0.96 ≈ 130
• B = 255 × (1 − 0) × (1 − 0.04) = 255 × 1.00 × 0.96 ≈ 245

The result is rgb(59, 130, 245), a bright medium blue.

Why CMYK and RGB exist as separate colour models

RGB (additive colour) — screens work by emitting light. Red, green, and blue channels combine additively: maximum values of all three produce white (full brightness). Zero in all three channels is black (no light emitted). RGB is the native colour space for displays, cameras, and web graphics.

CMYK (subtractive colour) — printers work by layering inks that absorb certain wavelengths of reflected light. Cyan ink absorbs red light; magenta absorbs green; yellow absorbs blue. When you add more ink, less light is reflected back and the colour gets darker — which is why adding all three primaries at full values produces a muddy dark brown rather than a pure black. That is why printing adds a separate Key (black) ink: it is cleaner, cheaper, and more controllable for text and dark areas than trying to mix process black from C, M, and Y.

The mathematical conversion between them (the formula above) works by reversing the subtractive process, but it is an approximation. Real printing is device-dependent — ink density, paper whiteness, and printing conditions all affect the final output. A CMYK file printed on a glossy magazine press will look different from the same file on an uncoated newsprint stock, even though the ink percentages are identical.

When to use this converter vs ICC profiles

Use this converter for:

• Quick screen preview of a CMYK brand colour
• Pulling a CMYK value from a style guide into a web mockup or Figma component
• Converting a known print colour to CSS for a web asset that approximates the print look
• Exploratory comparison when you do not need print-accurate matching

Use ICC profiles when:

• Preparing files for a specific printer or press that requires colour-managed proofing
• Matching a brand’s exact Pantone or press specification on screen
• Working in Adobe Photoshop or Illustrator with a calibrated monitor and soft proofing enabled

ICC profiles embed device-specific colour transformations that account for ink gain, paper colour, and press characteristics. The mathematical formula this tool uses makes none of those corrections, so the screen preview is a close but not exact representation of how the ink will appear when printed.

Common reference conversions

Note that rich black (high ink values across all channels) and process black (K only) both mathematically produce rgb(0, 0, 0), but they look very different on press — rich black appears denser on large fills.