Foal Coat Color Probability Calculator
This calculator uses three major loci: Extension (E/e), Agouti (A/a), and Cream (Cr). It estimates probabilities using Mendelian inheritance and reports likely foal colors.
How this horse coat color calculator works
Horse color genetics can look complicated, but a large share of common coat outcomes can be predicted with a few key genes. This calculator focuses on three foundational loci that have strong effects on base coat color:
- Extension (E/e) determines whether black pigment can be produced.
- Agouti (A/a) controls where black pigment appears on the body.
- Cream (Cr) dilutes pigment and can create single- and double-dilute colors.
By combining parent genotypes and applying Mendelian probabilities at each locus, the tool reports likely foal phenotypes such as chestnut, bay, black, palomino, buckskin, cremello, perlino, and smoky cream.
Quick genetics primer
1) Extension (E/e)
The E allele allows black pigment (eumelanin). The e allele is recessive and blocks black pigment when homozygous. So:
- EE or Ee = black pigment possible
- ee = red-based coat (chestnut family)
2) Agouti (A/a)
Agouti only visibly affects horses that can produce black pigment (E_). It restricts black pigment to points (mane, tail, lower legs), producing bay patterns.
- A_ with E_ tends toward bay
- aa with E_ tends toward black
- In ee horses, Agouti is usually hidden by red base color
3) Cream (N/Cr)
Cream dilution is dose-dependent:
- NN = no cream dilution
- NCr = single dilute (e.g., palomino, buckskin, smoky black)
- CrCr = double dilute (e.g., cremello, perlino, smoky cream)
Interpreting calculator results
The output lists predicted coat colors with percentages. These percentages represent statistical expectations over many foals, not a guarantee for one individual foal. In real breeding, each foal is one random draw from the probability distribution.
You will also see genotype combinations behind the scenes. Different genotypes can map to the same visible color, which is why phenotype percentages are often easier to use for planning.
Example scenarios
Example A: Buckskin potential
If one parent is Ee Aa NCr and the other is Ee Aa NN, you may see a mix of bay/chestnut/black families, with some single-dilute outcomes. Buckskin appears when a bay-base foal inherits one cream allele.
Example B: Double-dilute chance
If both parents carry one cream allele (NCr × NCr), there is a classic 25% expectation for CrCr at the cream locus, which can produce cremello, perlino, or smoky cream depending on base color genes.
Important limitations
This calculator is intentionally focused and does not include all color-modifying genes. Real-world coat appearance can also be affected by:
- Gray (G) progression with age
- Dun, Champagne, Silver, Pearl, and Mushroom modifiers
- Roan and white pattern genes (e.g., tobiano, frame overo, sabino, leopard complex)
- Sooty, pangaré, seasonal coat changes, and environmental influences
For breeding decisions, genetic testing through a reputable equine lab is strongly recommended.
Bottom line
A horse coat color calculator is a practical way to visualize probability before a breeding cross. Use it as an educational planning tool, then combine results with pedigree history and DNA testing for the most accurate expectation.