Burmese Cat Colours Calculator

A male cat has only 1 X chromosome.

If a male kitten receives an X chromosome with the red factor from his mother, he will be red or cream.

If he receives an X chromosome without the red factor from his mother, he will not be red. In that case, his ordinary base colour will be visible: brown, chocolate, blue or lilac.

The father gives his son a Y chromosome, because the Y chromosome makes the kitten male. But this does not mean that the father gives his son only the Y chromosome and nothing else.

The father also passes many ordinary genes to his son. These genes are not located on the X or Y chromosomes. They include the genes for brown or chocolate, and the genes for dilution.

These ordinary genes form the hidden base under red or cream.

Imagine this mating:

• the father is brown and does not carry chocolate;
• the mother is red.

A male kitten is born.

From his mother, he receives an X chromosome. If this X chromosome carries the red factor, the kitten will look red.

From his father, he receives a Y chromosome, so he becomes male.

At the same time, the kitten receives ordinary base colour genes from both parents. These genes are not located on the X or Y chromosomes. One copy comes from the father and one copy comes from the mother.

Because the father is brown and does not carry chocolate, he can pass only a brown base gene. If the mother also passes a brown base gene, the male kitten will be genetically brown based.

As a result, the kitten looks red because of the red factor on his X chromosome, but his hidden base is brown.

This is what the calculator calls:

Red (brown based)

It means a red male cat whose hidden base under the red coat is brown.

If one parent passes chocolate and the other parent passes brown, the kitten is still brown based, because brown is dominant over chocolate. In that case, the cat may look red but be genetically brown based and carry chocolate. A red cat is chocolate based only when it receives chocolate from both parents.

If a male cat is red or cream, he still passes one copy of his hidden base colour genes to his kittens. The final base of each kitten is determined together with the copy received from the mother. This base is not located on the X chromosome. It is carried by ordinary colour genes.

To his sons, a red or cream male passes a Y chromosome. This means his sons receive red or not red from their mother. But they still receive ordinary base colour genes from their father.

To his daughters, a red or cream male passes his X chromosome. If the male is red or cream, this X chromosome carries the red factor. This means all of his daughters receive the red factor from him.

What happens next depends on the mother.

If the mother has no red factor at all, meaning she is not red, not cream and not tortie, daughters from a red or cream male will always be tortie, because they receive:

• red factor from the father
• not red from the mother

Which tortie colour they become depends on the hidden base and dilution. It may be Seal Tortie, Blue Tortie, Chocolate Tortie or Lilac Tortie.

If the mother is tortie, the situation is different. She has one X chromosome with the red factor and one X chromosome without it. A daughter from a red or cream male may therefore be tortie if she receives the non red X from her mother, or red or cream if she receives the red X from her mother.

If the mother is red or cream, all daughters will be red or cream, because they receive the red factor from both parents. Whether they are red or cream depends on dilution.

This is why a red or cream male is very important in colour calculation. He gives the red factor to his daughters through the X chromosome, but he also gives his hidden base to all kittens through ordinary genes.

A red male may look red, but he can still pass one copy of his hidden base colour genes to his kittens.

The kitten’s final base is always the result of two inherited copies, one from each parent.

He can pass his X chromosome with the red factor to his daughters.

But he can pass ordinary colour genes, such as brown or chocolate, and dilution genes, to both sons and daughters.

This is why 2 red males may look similar, but produce different kitten colours.

One may be:

Red (brown based)

Another may be:

Red (chocolate based)

Visually, both are red. Genetically, they are not the same.

Cream is the dilute form of red. It is not a separate base colour. The hidden base underneath cream still depends on the brown or chocolate genes and the dilution genes inherited from both parents.

If red is on a brown based background with dilution, the calculator calls this:

Cream (blue based)

Why blue based? Because brown with dilution becomes blue.

If red is on a chocolate based background with dilution, the calculator calls this:

Cream (lilac based)

Why lilac based? Because chocolate with dilution becomes lilac.

Visually, both cats may look cream. But genetically, they are different, and this can change the possible colours of their kittens.

A female cat has 2 X chromosomes.

If neither X chromosome carries the red factor, the female will not be red. Her ordinary base colour will be visible: brown, chocolate, blue or lilac.

If both X chromosomes carry the red factor, the female will be red or cream. A red female may be brown based or chocolate based, and she may carry dilution without showing it. A cream female is already dilute, so her hidden base may be blue based or lilac based.

If the red factor is present on only 1 of her 2 X chromosomes, the female becomes tortie.

This happens because different X chromosomes are active in different areas of the coat. In some areas, red or cream is visible. In other areas, the base colour is visible.

This produces:

• Seal Tortie
• Blue Tortie
• Chocolate Tortie
• Lilac Tortie

This is why tortie cats are almost always female.

Very rarely, tortie males are born with an XXY chromosomal anomaly. Such males may look tortie, but they are generally infertile and are not used for breeding.

When you choose red or cream in the calculator, the visible colour alone is not enough.

The calculator needs to know which base is hidden under that red or cream coat. This hidden base is not always possible to know from appearance alone, especially when the parents may carry hidden chocolate or dilution.

That is why it offers these options:

Red (brown based)

A red cat with a hidden brown base.

Red (chocolate based)

A red cat with a hidden chocolate base.

Red (brown or chocolate base uncertain)

A red cat whose hidden base is not known. For this option, the calculator estimates the result by assuming a 50% probability of a brown based genotype and a 50% probability of a chocolate based genotype.

Cream (blue based)

A cream cat with a hidden blue base.

Cream (lilac based)

A cream cat with a hidden lilac base.

Cream (blue or lilac base uncertain)

A cream cat whose hidden dilute base is not known. For this option, the calculator estimates the result by assuming a 50% probability of a blue based genotype and a 50% probability of a lilac based genotype.

If the base is unknown, the calculation of possible kitten colours can only be approximate.

If both parents are heterozygous for the brown or chocolate locus, several hidden bases may be genetically possible. In such cases, the result depends on the base you choose, and the exact base may require genetic testing, known parent genotypes, or reliable breeding information.

The X chromosome does not carry the whole coat colour. It only carries red or not red.

Brown, chocolate and dilution are inherited through other genes, with one copy coming from each parent.

A male cat gives his son a Y chromosome, but he also gives him ordinary colour genes.

A red or cream male gives his daughters an X chromosome with the red factor. This is why daughters from a red or cream male and a non red female will always be tortie.

This is why a red or cream Burmese may have a hidden base that is not visible in the coat. That base is formed by genes inherited from both parents and is very important when calculating future kitten colours.

For a deeper explanation of Burmese cat genetics, colour inheritance and inherited health risks, read Sergej Reiner’s dedicated genetics guide.

Sergej Reiner is the author of this article and the Burmese cat genetics guide, an experienced felinologist, Burmese cat breeder and founder of Royal Esprit. He is also preparing a book on Burmese cat genetics, written in clear and accessible language.