A cat's colour is set by several genes. A kitten gets one copy of each gene from the sire and one from the dam, which is why one litter can have kittens of different colours.

• Red is sex-linked. Its gene is on the X chromosome. A male gets his X chromosome only from his mother, so the sons of a red female are red or cream. Only a female can be tortie: she has two X chromosomes, one with the red gene and one with black. Only one of them works in each cell, so red and black areas of coat are mixed in patches.
• Blue and cream, solid and classic tabby are recessive. They only show if the kitten gets the gene from both parents. A parent can carry such a gene without showing it: two black classic tabby parents can have a solid blue kitten.
• Silver, white spotting, white, ticked and mackerel tabby are dominant. A silver or smoke kitten can only be born if at least one parent is silver.
• Mackerel and spotted are shown as one row. The genetics of the spotted pattern aren't fully understood, and a kitten's pattern is often recorded inaccurately at 2 months.
• Reds and creams always show a pattern, even without the agouti gene. So genetically "solid" red kittens appear in the table in the row for their pattern. Solid black and blue cats have no pattern, though faint "ghost" stripes sometimes show.
• Silver and white spotting don't depend on sex or the other colour genes, so they're shown in a line under the table: with silver, solid black becomes black smoke and black classic tabby becomes black silver classic tabby.

Hidden genes. The calculator only knows the parents' colours. Mark hidden genes with the Carries blue, Carries solid and Carries classic tabby boxes: without a tick it assumes the parent doesn't carry them.

Chocolate, lilac, cinnamon, colourpoint and golden aren't recognised in Maine Coons by FIFe and WCF, so the calculator doesn't include them. What the letters and numbers in an EMS code mean is explained on the Colour codes page.

A percentage in the table is the probability for each kitten, not the share of the litter. It's a forecast, not a guarantee.