foal colour calculator

How this foal colour calculator works

This calculator uses basic Mendelian inheritance to estimate colour probabilities from two parents. For each gene, the sire and dam pass one allele to the foal. The tool combines all possible allele pairs and reports likely visible coat colours.

The model is designed for practical planning and education. It focuses on five major genes that strongly influence common base colours and dilutions: Extension, Agouti, Gray, Cream, and Dun.

What each gene controls

1) Extension (E/e)

Extension controls whether black pigment can be produced. Foals with e/e are red-based (chestnut family). Foals with at least one E can produce black pigment and then depend on other genes for final colour.

2) Agouti (A/a)

Agouti affects where black pigment appears. On black-pigment horses, A restricts black mostly to points (bay), while a/a allows full-body black expression.

3) Gray (G/g)

Gray is dominant. A foal with one gray allele (G/g) will usually gray out over time, regardless of base coat. The foal is still born with an underlying colour, which this calculator shows in parentheses.

4) Cream (N/Cr)

Cream is an incomplete dominant dilution. One copy often creates single-dilute colours (palomino, buckskin, smoky black). Two copies create double-dilute colours (cremello, perlino, smoky cream).

5) Dun (D/d)

Dun is a dominant dilution and pattern modifier associated with primitive markings. Depending on base coat, dun can produce colours such as red dun, bay dun, grullo, dunskin, and dunalino.

Reading your results

• Top section: final phenotype probabilities (what colour the foal is likely to appear).
• Gene-level odds: possible foal genotypes for each individual gene.
• Percentages: expected long-run frequencies, not guarantees for one foal.

Important limitations

Real horse colour genetics can involve additional genes and modifiers not included here (for example, silver, champagne, pearl, roan, and white patterning genes). Testing through a reliable equine genetics lab remains the best source of breeding certainty.

Even with complete genotype data, expression can vary in shade and pattern intensity. Use this calculator as a practical estimate tool, not as absolute prediction.

Best practices for breeders

• Use DNA test results whenever possible instead of visual guesses.
• Track both genotype and phenotype in your breeding records.
• Prioritize health, temperament, and conformation over colour alone.
• Consult breed-specific registries for naming and classification standards.