This page uses a simplified independent-assortment model (E, A, Cr). Grey (progressive) and some patterns need other genes—see the note below.
Parents
Sire (father)
Dam (mother)
Foal color probabilities
Top outcomes
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| Color / pattern | Probability | Preview |
|---|
Punnett squares (this pairing)
Extension (E) cross — rows = sire gamete, columns = dam gamete.
Agouti (A) cross
Common crosses (reference)
| Pairing | Typical result |
|---|---|
| Bay × Chestnut | Often ~50% bay-type, ~50% chestnut if sire carries e |
| Chestnut × Chestnut | Always chestnut (ee) |
| Black × Black (both E_aa) | Black foals; no bay without A |
How horse coat genetics work (basics)
Extension (E): lets black pigment be produced in hair (E) vs red/chestnut only (ee). Agouti (A): on black pigment, restricts it to mane/tail/legs (bay) vs solid black body (aa). Cream (Cr): dilutes pigment—one dose on chestnut → palomino; on bay → buckskin.
Dominant vs recessive
E and A are dominant in the usual sense used here; e and a are recessive. Many horses are heterozygous (e.g. Ee)—testing reveals what they can pass on.
Common colors
- Bay — black points, red body (E_ A_).
- Black — E_aa.
- Chestnut — ee.
- Grey — often dominant G; not included in this calculator’s core math.
Embed
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FAQ
- How to predict horse color?
- Use known parent genotypes (ideally from testing) and Mendelian rules for major genes—this tool demonstrates that logic.
- What genes determine coat color?
- Extension, Agouti, Cream, and others (grey, silver, roan, etc.) interact; this page focuses on E, A, and optional Cr.
- Can two chestnut horses produce black?
- No—both parents must contribute e, so the foal is ee and cannot show black-based body pigment as in black or bay.
- What is the rarest horse color?
- Depends on breed and test frequency; very dilute or unusual pattern combinations can be rare. Here, outcomes under ~15% are tagged “rarer.”