CMYK to RGB Color Converter
Convert CMYK color values to RGB for use on screen or in web design.
How to use this tool
- Enter cyan, magenta, yellow, and key (black) percentages (0–100 each).
- The tool calculates the corresponding R, G, B values (0–255).
- Copy the rgb() string into CSS or your image editing software.
Convert print CMYK color values to RGB for display on screens, websites, or digital media.
Formula
Given C, M, Y, K each as percentages (0–100), normalize to 0–1: c = C/100, etc.
R = round(255 × (1 − c) × (1 − k))G = round(255 × (1 − m) × (1 − k))B = round(255 × (1 − y) × (1 − k))
How it works
CMYK-to-RGB reverses the subtractive model: each CMYK ink channel reduces the corresponding light channel, while the Key (black) channel attenuates all three equally. Multiplying (1 − ink) by (1 − key) gives the fraction of full-brightness light remaining in each channel, which is then scaled to the 0–255 byte range.
A common mistake is treating the inputs as fractions already in 0–1 rather than percentages in 0–100, which underestimates the ink coverage by a factor of 100 and produces near-white output regardless of the intended color. Always divide each CMYK input by 100 before applying the formula.
Worked example
Convert CMYK (0%, 100%, 100%, 0%) — pure red in print — to RGB
- Normalize: c = 0.0, m = 1.0, y = 1.0, k = 0.0.
- R = round(255 × (1−0) × (1−0)) = round(255) = 255.
- G = round(255 × (1−1.0) × (1−0)) = round(0) = 0.
- B = round(255 × (1−1.0) × (1−0)) = round(0) = 0.
rgb(255, 0, 0)
Common mistakes to avoid
- Entering CMYK values as decimals (0 to 1) instead of percentages (0 to 100), producing near-white output for values like 0.5 instead of 50.
- Expecting a perfect round-trip from RGB to CMYK back to RGB -- the conversion is not perfectly reversible because CMYK has a smaller gamut.
- Forgetting that K = 100% alone produces black regardless of C, M, Y values -- setting C=M=Y=100% and K=100% results in the same black, not a darker one.
Key terms
- Cyan (C)
- The blue-green ink in CMYK that absorbs red light; 100% cyan removes all red from the output, leaving a blue-green color on white paper.
- Magenta (M)
- The pink-red ink in CMYK that absorbs green light; combined with yellow it produces red, and with cyan it produces blue.
- Yellow (Y)
- The ink in CMYK that absorbs blue light; theoretically C+M+Y at 100% should yield black, but in practice produces a muddy brown, which is why the K channel exists.
- 255 byte range
- The 0–255 integer scale used for each RGB channel in digital displays, derived from 8 bits per channel (2⁸ = 256 possible values).
Frequently asked questions
- What does Key mean in CMYK?
- Key refers to the black ink plate, used in offset printing to sharpen detail. It is called Key because the other plates are keyed (aligned) to it.
- Why convert CMYK to RGB?
- If you receive a CMYK color from a print designer and need to use it on a website, you convert it to RGB which screens understand.