Work out rgb to cmyk instantly with clear inputs, formula shown and shareable results.
Black is one minus the largest normalised channel, and each subtractive ink is the shortfall of its complementary channel scaled by one minus black. This naive conversion ignores ink and paper profiles, so it gives the right structure but a print house will still need an ICC-managed conversion for accurate colour.
Key
K = 1 - max(R, G, B), with channels normalised to 0-1
Inks
C = (1 - R - K) / (1 - K), and similarly for M and Y
K = 1 - max(R, G, B), with channels normalised to 0-1. Black is one minus the largest normalised channel, and each subtractive ink is the shortfall of its complementary channel scaled by one minus black.
This naive conversion ignores ink and paper profiles, so it gives the right structure but a print house will still need an ICC-managed conversion for accurate colour.
Enter red, green, blue. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.