Predict foal coat color probabilities using four major loci: Extension (E/e), Agouti (A/a), Cream (Cr), and Gray (G/g). Choose each parent's genotype and click calculate.
Sire (Parent 1)
Dam (Parent 2)
Educational model only. Real-world color outcomes can be influenced by additional genes (dun, silver, champagne, roan, tobiano, etc.), testing uncertainty, and registration naming conventions.
How this horse genetic color calculator works
This calculator estimates foal color probabilities by combining classic Mendelian inheritance across four independent loci. For each gene, the sire and dam each contribute one allele. The calculator builds all possible combinations, totals probabilities, and then translates those genotypes into likely coat-color phenotypes.
It is most useful when you already have DNA test results and want a quick probability snapshot before breeding decisions.
Core genes included in this model
1) Extension (E/e)
The Extension locus controls whether a horse can produce black pigment (eumelanin).
- E allows black pigment.
- e blocks black pigment when homozygous (e/e), producing a red-based horse.
If a foal is e/e, base color is chestnut/sorrel regardless of Agouti genotype.
2) Agouti (A/a)
Agouti controls where black pigment appears, but only if the horse has at least one E.
- A restricts black to points (mane, tail, legs) = bay pattern.
- a/a allows full-body black pigment = black base.
3) Cream (Cr)
Cream is an incomplete dominant dilution gene. Effects depend on whether a horse carries one or two copies.
- N/N: no cream dilution.
- N/Cr: single dilution (palomino, buckskin, smoky black).
- Cr/Cr: double dilution (cremello, perlino, smoky cream).
4) Gray (G/g)
Gray is dominant. A horse with G/G or G/g will progressively gray over time, regardless of underlying birth color. This calculator reports gray as an overlay, such as Gray (born bay).
Interpreting your results
After calculation, you get two useful outputs:
- Phenotype probabilities: the chance of each visible color category.
- Genotype probabilities by locus: expected inheritance percentages for Extension, Agouti, Cream, and Gray.
This gives both breeder-friendly color expectations and genetics-focused detail for recordkeeping.
Example breeding scenarios
Example A: Bay × Chestnut
If one parent is E/e A/a N/N g/g and the other is e/e A/a N/N g/g, you should expect a mix of chestnut, bay, and potentially black offspring depending on which E and A alleles are inherited.
Example B: Buckskin × Palomino
When both parents carry one cream allele (N/Cr), offspring can be no-cream, single-cream, or double-cream at roughly 25% / 50% / 25% for the cream locus itself. Final color still depends on Extension and Agouti.
Important limitations
- Not all coat color genes are included.
- Pattern genes (tobiano, frame, splash, leopard complex) are excluded.
- Shade variation (light/dark bay, liver chestnut, sun fading) is not modeled.
- Gray progression timing is not predicted.
For breeding plans, combine calculator output with full-panel genetic testing and guidance from a knowledgeable veterinarian or equine genetic consultant.
Quick glossary
- Genotype: the allele pair at a gene (example: E/e).
- Phenotype: observable color (example: buckskin).
- Dominant: one copy is enough to show effect.
- Recessive: usually requires two copies to show effect.
If you want to expand this tool later, the most practical next additions are Dun (D), Silver (Z), and common white-pattern loci.