This is a naive conversion without an ICC colour profile. Screen RGB is additive light and print CMYK is subtractive ink, so their gamuts do not overlap. Treat these numbers as a starting point and confirm against a printed swatch or a soft proof before going to press.
Tool guide
About RGB to CMYK Converter
An RGB to CMYK converter turns the three 0-255 values you read in Photoshop, Figma, or a screen color picker into the four ink percentages a press uses: cyan, magenta, yellow, and key black.
Each channel has its own number box and slider, so you can change one channel at a time and watch the CMYK values respond live. A direction button flips the tool around for CMYK to RGB.
How to convert RGB to CMYK channel by channel
- Type the R, G, and B values from your design software into the three number boxes, or set them with the sliders.
- Move a single slider and watch the CMYK output update, the fastest way to see which ink that channel drives.
- Copy the four CMYK percentages into your document color settings or your notes for the print shop.
- Use the direction button to switch to CMYK to RGB when you start from ink values instead.
When you would use it
- Checking color values in a photo or raster asset before it enters a layout headed for print.
- Verifying a fill color in a design file before export, so nothing ships with a screen-only value.
- Seeing how one channel moves the black plate, useful when prints keep coming back too dark.
- Explaining why a saturated screen color cannot be reproduced with four process inks.
How the math works
This is a naive conversion with no ICC color profile involved. The standard formula is a reasonable starting point, not a color-managed result.
- K comes from the strongest channel: K = 1 - max(R,G,B)/255, so lowering any channel can change the black plate.
- Each ink is then computed relative to that black, for example C = (1 - R/255 - K) / (1 - K).
- Pure black gives K = 1 and zero for the other inks, since all density lands on the key plate.
- Output is four percentages from 0 to 100, usually rounded to whole numbers.
RGB to CMYK FAQ
- Why do printed colors look duller than my screen?
- RGB is additive light from a display, CMYK is subtractive ink reflecting room light, and the two gamuts do not overlap. Bright blues, vivid greens, and neon shades are out of gamut and print noticeably darker and grayer.
- Can I trust these numbers for a final print job?
- Treat them as a starting point. Final sign-off should rest on a printed ink swatch book or a soft proof made with the correct ICC profile.
- Why does changing green affect K?
- K is derived from the largest of the three channels. If green is the highest, lowering it raises K and darkens the whole mix.
- Are my color values uploaded anywhere?
- No. On wetool.site the conversion is local arithmetic in your browser, so the values you enter are never sent to a server.
Naive conversion vs color-managed conversion
A naive conversion is pure arithmetic on the three channels and always returns the same answer for the same input. A color-managed conversion maps colors through an ICC profile describing a specific press, paper, and ink set, so its output differs by job. Use this page to check values, and your ICC workflow when the result must match on paper.
Reading the sliders like plates
Each slider stands for one light channel, and every move redistributes density across four ink plates.
- Set two channels to 255 and sweep the third to isolate which ink that channel controls.
- A pure primary such as 0,255,0 needs heavy coverage on one or two plates, which is why saturated screen colors become multi-plate overprints.
- When all three channels move together the inks stay balanced and mainly K changes, the neutral gray path.
What this page does not do
Knowing the limits keeps the numbers honest and avoids surprises at the press.
- No ICC profile import, so no press, paper, or ink condition is taken into account.
- No image upload or in-page color sampler; pick the color in your design software and type the values here.
- No Pantone or spot color lookup, so a spot ink match still comes from a physical guide.